From another sticky post:
Due to a mass of trolling, only established posters are able to post in non-newbie sections. You are considered "established" if you have spent 4 hours online and have made 5 posts.

If you have really good posts, you can post a request for preemptive whitelisting in the appropriate topic.

Also:
- You must have made one post in order to send PMs.
- You need 10 posts to put a link in your signature.
- You need 50 posts to put an image in your signature.

Note that it may take up to 10 minutes for your PM or posting permissions to be granted.