Lately I've been having this problem where I make these fleshed out characters with various backgrounds, and create a setting for the story to take place and go into great detail about the aspects of my setting. But then I'm not sure where to go from there. I have ideas for what conflicts the characters will run into but I have trouble creating an overall conflict and main antagonist. My story is about a werewolf and I guess you could say the series will be classified as urban fantasy since it is basically in our world except the supernatural are real. But a lot of urban fantasy deals with mysteries or supernatural cops and bounty hunters hunting down people. I kind of wanted to go for a more urban epic fantasy with a lot of traveling and plot that stretches over all the books, not a different plot for each book. So when you have trouble with creating your antagonist, conflicts, and overall plot and goals of your main characters, what do you do? Where do you get your inspiration? How do you overcome this specific type of writer's block?
It sounds like you've got the cart before the horse here. You don't have a main antagonist or an overall plot, and your MCs don't have primary goals, but you have a series in mind? You shouldn't be planning a series at this point. You don't have enough material, enough stuff for even one novel, let alone a series. You shouldn't be planning a series until you can complete one novel. I mean, go ahead and dream about writing a series - tons of people do, including lots here on these forums - but that dream doesn't give you the material you need. I think you should gather enough material for one story and write that story, and if it organically grows into more than one novel, then fine; maybe you have the potential for a series. But don't start trying to write a series when you don't have enough ideas even for one novel. If you really have well-drawn characters and a setting, then just come up with some instigating event, a situation the characters are in that requires them to act in some way. Then start writing and see what they do. If you can't come up with a situation that requires your characters to act, they'll probably just sit there doing nothing and you don't have a story. So get them motivated and see what happens - your plot will evolve from that. I'm sorry if this sounds harsh. But it seems to me that you're starting off with very unrealistic goals.
It's weird... I almost have the opposite problem. It's really easy for me to come up with a detailed plot, but I'm not as good at having a detail setting and only somewhat decent at creating characters. I don't really know what to tell you. Usually my plots come to me, I kind of set aside time for myself to flesh out what I'm going to do. And before you know it I'm a week in and I have for the most part a very detailed overall plot to the story. I know one thing that helps is I watch a lot of TV, read a lot of books... and usually something inspires me. And you don't have to have the entire plot down in one go. You don't have to start at the beginning of the story either. You can start at a climactic point in the plot. Maybe an argument that two of the characters have, or a fight that two groups of people have. But as an example of how random things can inspire you... maybe I'd see the trailer to "Real Steel" and I'd think "you know... I want to put a scene where the MC and antagonist are in some kind of battle and the MC has to overcome his feelings of doubt and uncertainty that come from the gigantic crowd around them to win the battle." And your story would have nothing to do with fighting robots, but its just the idea of a battle that got you thinking of what you want your story to be. So I guess the thing to take away from this is that you don't have to start from the beginning. I don't think I've ever actually started my plots at the beginning. Just start thinking of cool "scenes" you would like to see happen in your story and try to figure out how your characters get to that point and also what happens as a result and BAM before you know it you have a plot.
I half agree with Minstrel on this one. I don't want to deter you from writing a series, mainly because I have a hard time taking interest in stand alone books period, as in, I don't think I could make myself do it. But without a plot, you really shouldn't be thinking so far ahead. Start with your first book, think of a (partially) stand alone plot, but leave some bigger themes open to elaborate on in later books in the series.
What are the main character's goals? What has or can impede the character in obtaining them? Maybe the goal is to simply survive. Maybed it's to visit every country in Europe before turning 25. That doesn't mean things can't crop up along the way. An antagonist can be more than an individual. It can be society, weather, time...who knows. Also, I am not saying this is you, but I've seen some writers who've created a character(s) they love and don't want to put them in situations where they truly suffer, and even perish. Just a few thoughts. Good luck moving forward.