Groups and permissions on this site are described here
Generally, you can PM me to get more permissions with a short description on why you need them. For example, if you are going to submit a skin to Downloads and want some PFS space, I can set you a "Skin Maker".Added 3 minutes later:
And, yes, submissions in Downloads are welcome from any registered members. They are checked and if everything is fine they are validated, or you will receive a PM with the reason otherwise.
May the Source be with you!