This is my comprehensive, generic guide on how to install mods of all types, with generic instructions that should still be accurate even with mod version changes, new basegame versions and even for mods that don't yet exist.
There is also a whole section on how to make your own simple mods.
Be sure to watch the whole of Section 1, before moving to the section that covers what you want to achieve!
Section 2: Installing Single folder Mods (XAI, XLRP). 06:09
Section 3: Folder based CAB Mods (BEX, BEXCE, BTA3062, The Hyades Rim). 11:35
Section 4: Installer Based Mods (ROGUETECH). 19:20
Section 5: Making your own mods. 24:33
Section 6: Tricks and Tips for backing up mods. 39:04
Note to mods: I will update the main pin in the mods forum to include this later, but would like to keep this topic here for feedback and visibility.
I hope this helps