First of all, are you converting your RAW files to a .jpeg after you are done with your PP? I don't want to assume anything, hence the question.
Secondly, do you belong to a photo sharing site like Flickr? If not, that is the easiest way to get photos onto POTN, though not the only method. I've noticed different people use different methods. Flickr is what I started with and it is pretty easy.
I'll watch for your reply and then add info if you need it, rather than bore you with a lengthy explanation of stuff you already know.
Kim (the male variety) Canon 1DX2 | 1D IV | 16-35 f/4 IS | 24-105 f/4 IS | 100L IS macro | 70-200mm f/2.8L IS II | 100-400Lii | 50 f/1.8 STM | Canon 1.4X III
RRS tripod and monopod | 580EXII | Cinch 1 & Loop 3 Special Edition | Editing Encouraged