Just open a post and find the "Actions" bar at the bottom right. Click on it and select "Reply." After that it's pretty obvious.

but I think you may be wondering how to put up an ad or profile.

 
A good place to start is the FAQ for Newbies that you'll find on this page.   Read through it first and then see if you still have specific questions, you can ask them on here.

 
On the question of a profile, TER is a review site, not an escort mall.   That means you only get a profile when a client reviews you, and they set up the profile.

 
Welcome to TER and best wishes for success.