See [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) then the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information.
There is also ongoing discussion for the extend layer, at the [Colemak Forum](https://forum.colemak.com/topic/2327-developing-an-extend-layer-for-the-katana60/)