Hello, and welcome! You will be able to post writing in the workshop after you have been a member for 14 days, made 20 posts, and offered two constructive critiques of other members' work. Please review the forum rules here for more information on using the workshop: https://www.writingforums.org/rules/
Welcome to the forum, there are some good people here. My advise to you would not to simply register with the motive of receiving feedback and critiquing other people's writing simply for the sake of necessity. I feel this may not always be helpful to those that have made submissions there, so try and critique them in a manner in which you'd appreciate (and not just in a complimentary sense) in regards to your own content. Find some writing you enjoy on here and try and offer improvements to whatever you feel they can improve on. I personally found it difficult to make criticisms to others in genres I wasn't all too interested in, so go forward with an approach where you feel like you're already enthralled in what it is they have to say. I suppose I'm saying nothing that cannot be found in the rule section, already, but there are some interesting people here to be met that are capable of offering you insight/experience you never may have expected. My advice is to come with a sincere approach with who you are and your goals and to ignore any cynicism you may face along the way. So based on that, what ideas do you wish to promote in your writing and how would you categorise it? How much progress have you made? As I've found in Linux communities, it's best to have something to offer, be it your opinions, perspectives or critiques, regardless of whether it has anything to do with the mandatory rulings here based upon workshop entries. Hell, you'll find people you're genuinely interested in before long and find inspiration simply conversing with them. When I first joined, I found it pretty difficult to navigate my way around and determine who's who and what they stood for, but this is definitely a good place to be if you take your craft seriously. Get involved in whichever way you find interesting...and welcome, once again.