I would personally un-mark, save, and the re-mark the folder as read only, then I would check the individual files. This is the most crucial step, a hint of paranoia is an advantage.

If the box is already ticked don't trust your computer. Set the entire proto folder to read-only, the proto folder is under Fallout2/data/proto you simply need to right click on the folder and tick the read only box.For the PowerPC Mac OS X port, it's generally recommended to instead install them to ~/Library/Application Support/Fallout2/DATA/, but installation is otherwise the same.

Fallout2/data/data, yes two data folders are supposed to be there, do not concern your self with the second unless your specific mod read me says so. Install the mod you downloaded, most of the time you simply copy and paste the files into your FO2 directory, some people get confused with the directory structure i.e.If you're using the PowerPC native Mac OS X port, you instead want to right click on the app and click 'Show Package Contents', then navigate to /Contents/Resources/GameData/. Check your FO2 folder, for a file called patch000.dat, if you have it delete or rename it.Install the version of Fallout 2 that takes up the largest amount of space i.e.Generally mods contain a 'readme' file with a guide, I would recommend checking that out, before proceeding with this general guide, also before you attempt to install a mod, make sure FO2 works fine vanilla:

How to manually download mods fallout 4