When you go to the trainer Menu does it show INH or ACT? If it shows INH hit the + key for Data Input, this will change it to ACT. Once its Activated and when you pull up on the trainer switch it will show it ON above the word ACT.

I believe by default channels 1, 2, 3 and 4 are activated. This is indicated by the arrows below these 4 channels. Channels 5 through 8 have the arrows above the channel numbers. To activate any channel cursor over and move the arrows below the channels you want to activate or allow the trainee to have control of.