Is it possible to change the style CSS?

Hi,
I've been designing clients phpBB forum styles for years but this is my first time starting my own forum and using a hosted service so it's new and different to me, is there a way to access/change the CSS for the style?

The forum I've set up looks fine on the computer, but on my phone parts of it are overlapping others, text hanging out of boxes etc, so I just want to make it look as good responsively as it does on the computer.

Also a second question, I've just seen the HitSkin website and the section that allows a skin to be submitted, is that basically just CSS changes? or is there anywhere to submit a complete style?

Yes AP-->

Correct, CSS and images are uploaded to Hitskin, If you have JavaScripts and modified templates they will not be uploaded.

Thanks guys, looks you have a much more pro setup here than at TapaTalk, great work.

Is this solved, @Mark.G?

If so, please change the topic icon to "solved". Thank you.