Solder the Pi Zero W headers (if your version didn't come pre-soldered) and solder LED breakout board if needed. Details are available at https://github.com/deckerego/tally_pi/blob/master/docs/HARDWARE.md

Instructions at https://github.com/deckerego/tally_pi/blob/master/docs/INSTALLING.md with optional steps to make your SD card last a bit longer.

See https://github.com/deckerego/tally_pi/blob/master/docs/HARDWARE.md for details - this is optional, but highly recommended.

If you want to use OBS to control your tally lights, follow https://github.com/deckerego/tally_pi/blob/master/docs/OBS.md to install the OBS script. Bear in mind this is a script and not a plugin - so use the Scripts dialog to configure and control your lights.