How do I use this?

[idesignstuff]

How do I use this?

[snsten]

This automatically pulls the zmk firmware to build along with the specific configuration files nothing extra is required.
You can fork this repo which will run actions in your gh account at the end of the run a firmware artifact will be generated.

After that you can download the firmware.zip file from actions tab which has 3 uf2 files for left, right and reset.
See the actions docs for steps to download it.

[idesignstuff]

While it builds for me in your repo, my fork fails.

The debug shows this:
"devicetree error: /__w/Klein-zmk/Klein-zmk/config/boards/shields/klein/klein.keymap:43 (column 121): parse error: expected number or parenthesized expression"

Is it loading the wrong klein.keymap?
My Line 43 looks like this:
&lt MEDIA ESC &lt NAV SPACE &lt BLU TAB &bootloader &kp MUTE &lt SYM RET &lt NUM BKSP &lt FUN DEL

[idesignstuff]

This is just me being a beginner.