The method of retrieving a device handler from Github?

I followed Aeotec’s directions for Smart Switch 6 device handler in GitHub. Also Smartthings directions. However on GitHub page where the handler code was there was no way to “save” it. Trying to learn this. Where in the community is this information?

This link should help get you started (note that the instructions related to the SmartThings pp are for the old “classic app”, so some things there might be a little different, but the instructions for using custom DTH are mostly the same.