Easy setup:

1) Download and unpack ironwail (best engine).

2) Copy id1/ (from your official Quake install directory) to your ironwail directory

3) Launch ironwail

Adding and launching a mod:

1) Unpack the mod into your ironwail directory

2) Launch ironwail

3) select the add-on

If you have quake on steam, ironwail will automatically detect it.

If you want to directly launch into a mod you can create a shortcut or use command-line parameters.