Unfortunately, Dreamwidth isn't like Tumblr - there isn't infrastructure for anonymous post submissions, only anonymous comments. So if you want to post fanwork to the community itself, you're going to need to make an account.
After you make an account, you need to join the comm - there's a link to join on the profile. After you join, the profile will have a link that says "Post to community", and you can do it through there.
Re: Mod Note
Unfortunately, Dreamwidth isn't like Tumblr - there isn't infrastructure for anonymous post submissions, only anonymous comments. So if you want to post fanwork to the community itself, you're going to need to make an account.
After you make an account, you need to join the comm - there's a link to join on the profile. After you join, the profile will have a link that says "Post to community", and you can do it through there.