You should read
this guide, it explains how to configure IntelliJ and how to run the bot in developer mode so you can test the bots you write.
I also recommend reading
this one, it explains the bot manifest which is how you specify if your bot is for woodcutting, mining, agility, etc. as well as other things such as the name or description.
The tl;dr is run RuneMate with the argument -sdk and in the settings specify where your source code is being compiled.