You can only post in the Newbie and Local sub-forums till you have made one post and waited 4 hours. This post must be substantial: at least several sentences. The other two restrictions are you need 1 post to be able to send a PM and 10 posts to put a link in your sig. You can only post once every 360 seconds to start and there are a few other things that trigger this timer such as logging in and searching.
Info on forum ranks can be found here: https://bitcointalksearch.org/topic/forum-rankspositionsbadges-what-do-those-shiny-coins-under-my-name-mean-178608
From someone who hasn't read the rules on signup, thank you for this info. These are quite sensible rules for a forum like this. I hope I'll be able to contribute in a positive way.
Cheers,
OneTwoThree