Put Save On A USB (manual save, not auto.)
Put into Computer
Click on Horizon.
Go To the GTA V tool
Go on the right hand side and hit device explorer.
Click Games and then Double Click GTA V.
Mod it however you want.
REMEMBER TO SAVE OR IT DOESN'T WORK.
Once Done, Plug USB back into Xbox
Then, Go to System<Storage<USB
Find the now modded save, and move it over to your HDD
Load Up GTA V and you'll see that it's modded when you check your character's money.

What The Tool Contains-
Money Mods (Up to 2,000,000,000 2Billion)
Skill Mods (Stamina,Driving,Stealth, etc..)