Go to the file directory. Then download notepad++ and you can open and edit the JSON files. To save the changes as a mod, create a new folder and package it according to https://forums.uberent.com/threads/guide-getting-your-mod-on-pamm.55189/ You can look at other mod folders as well to see what other people did if you're having trouble.
Also important info for looking at other people's mods: They live here: Windows: %LOCALAPPDATA%\Uber Entertainment\Planetary Annihilation\ (Just copy-paste this in the address bar of Explorer) OSX: ~/Library/Application Support/Uber Entertainment/Planetary Annihilation/ Linux: ~/.local/Uber Entertainment/Planetary Annihilation If you've installed PAMM and installed mods, there should be directories called "client_mods" and "server_mods". If you have installed mods a long time ago, "client_mods" may simply be called "mods" instead. Mods that change unit stats are server mods.