I figured out the HTML uploads, just wondering how I would do a downloadable version? Would I put all unity files associated with game into a zip file and upload that?
The process is exactly what you described. You have to find all the files that are needed to run the game, put all those files in a zip file, and upload that.
You should probably check online what files are needed, to make your game portable.
For Unity, zip the entire file that appears after you build the project. Upload, and select it as executable on itchio and indicate what platform it will be running on. That’s it! If it’s a Mac build, zip the entire .app file, and then the same process.