1. Download Horizon from xboxmb (sorry, cant post external links, google it)
(optional) 2. Make a new profile on your Xbox, start up Halo 4 then sign out.
3. Move the profile you wish to mod to a usb (if you saved it to your HDD)
4. Take the usb out of your xbox and plug it into your pc.
5. Open up Horizon, and then open your profile. (Device explorer > Gamer Profiles > Double click the one you want to mod)
6. Click the contents tab on your profile in Horizon
7. Right-click 4D530919.gpd and then click replace
8. Replace it with the gpd I provided.
9. Save, Rehash, and Resign.
10. Enjoy!
Stupid thing I wrote about it:
Hi guys!
Just wanna post this, couldn't find a really "good" halo 4 gpd anywhere. So I bought a 1 month of horizon diamond and stuff and made my own. It has ALL (I'm pretty sure anyway) armors, including FOTUS and those pre-order exclusive ones. ALL commendations and specializations are completed, and all commendation + specialization unlockable armor customization options are unlocked. All achievements are unlocked too. The entire campaign is complete on Legendary on both co-op and solo. The service tag is "-_-" and it has all emblems. Some emblems are locked, the dev of the tool I used to get them is working on a fix. I initially made this for a friend who plays Halo 4 offline with his brothers and mates.
(sorry for craphouse quality on the pic)
edit: Offline only. Well, I haven't tried it online, but I wouldn't expect it to work, nor would I recommend doing so.