Are you trying to install mods, or make some?
To install mods, first extract them to the mod folder, users/appdata/roaming/Strive for Power 2/mods. Then, from the main menu mods section, select a mod on the right, press the left arrow, click ok, close, and restart the program.
To make a mod, the easiest way is to find one that does something similar to what you want to do and modify it.