Hi Ameliaa,
Welcome to the site. This thread is a good place to start, so read through it thoroughly. It is also worth doing your own research too using google to see sites which rank highly - if you are offering the more typical services, men can be lazy and tend to stick to whichever sites appear on the first search page.
It is worth nothing that some platforms are directories which means you can only advertise on it if you have your own website.
On a related note, if you are new to escorting, please do read the main SAAFE site, particularly regarding safety practises, screening and well, everything really. Be sure to work out your boundaries and limits, and refuse to budge. As a newbie, you will attract a lot of time wasters and randoms in the first few weeks who are keen to try it on.