Not to be a pedant or jerk, but just FYI, for questions utilizing an auxiliary comparable to the word "can" you want to reverse the pronoun with it, i.e. "When can I write posts in other threads" or "When can I write a post in another thread?"

I certified in teaching English a while back, and like to offer little bits of help where I can. Of course you could have just been typing fast, but just in case.

Now to answer your question: remember those terms about newbie status and what conditions you have to meet in order to get out of it and post elsewhere? You agreed to them in order even to sign-up and post at all, remember? Hint: "...14..."