Using this Trainer:
Launch the trainer first, then launch the Game and then Press F1 at the Main Menu.
Listen for "Activated".
Press desired option key
Numpad 1: Mega Health
Numpad 1: Mega Health - toggle on and your character has unlimited health. You need to be in the game and moving around for this to work.
Temporarily Disable Hotkeys:
To temporarily disable the Hotkeys, press CTRL-H after trainer is activated. You can use CTRL-H to re-activate the Hotkeys as well.
Creating Custom Hotkeys:
You can click on the actual option in the Trainer application itself to modify the Hotkey or the value used for that option. The trainer will save your hotkeys for you. To delete your Custom Hotkeys for this trainer, press the Debug Tab and then press CTRL-K and the keys will be deleted.