Hi Nuada, and welcome to WriteWords.
Yes, the site can be confusing at first, so if you get stuck just give us a shout.
It is best to join one of the Writing Groups and post a link to the piece of wrok you've uploaded, as it's liable to be overlooked in the Archive. Click on the orange 'Groups' tab at the top of the page and you'll see the list. Beginners and Short Story groups are very active and worth checking out, and don't be afraid to comment on group members work, that way they'll get to know you and reciprocate with feedback; and critiquing is a valuable skill for any writer to learn, and comes with practice.
As a trial member you can join one group and upload one piece of work, but if you become a full member you can join as many groups as you want, and move around the groups until you find one you like.
All the best with the writing,
- NaomiM