Very simple download instructions:
1. Open the "missions" folder from the zip file you downloaded.
2. Select all of the FMP missions from FMP #000 to FMP #044 and place them all into the mission folder that is located in this place: GTAV/scripts/MissionMaker/missions
3. Once that is done the missions should be working and once you are in game you can click F10 and play them conveniently.

ABOUT THE MISSIONS
There is 45 Missions in the pack right now! And the pack also has its own storyline, so please play the missions in order. The missions have their own startpoints set and you can start them anywhere anytime by just clicking F10 and then selecting the mission to play. My missions are labelled as FMP #001 FMP #002 etc. Saying this because there is also other creator missions that you might have.

Enjoy.
By the way Jesus is awesome.