Extract ALL files in the download, copy and paste the CH mcclauncher.exe into the games folder. Backup original mcclauncher.exe first.
c:\Program Files (x86)\Steam\steamapps\common\Halo The Master Chief Collection
Make sure the game folder and the trainer are excluded from anti-virus
www.cheathappens.com/virus_warning.asp
Then launch the game through Steam and select the bottom one to launch game
LinkActivate trainer only after selecting the game and loading into it.