To inflate the pillow open the valve cap and inflate by mouth. It is normal for some condensation to form.
To deflate or adjust the amount of air in the bladder, open the valve cap and push the green button in the very center of the valve.
For best performance, you want to use the smallest possible amount of air in the pillow and fill the remaining space with other soft stuff you might have with you, like a down jacket.
The best method is to stuff the soft stuff in the pillowcase between the bladder and the sleep surface. Then simply adjust the air in the bladder so the pillow is the correct height for you. Side sleepers will need more stuff/air to get the right height. The idea is to make it feel as much as possible like your pillow from home.
If the pillow valve is not holding air, the green release valve is not seating properly. To re-seat it, open the valve and push on and around the green button in the very center of the valve (the same one you use to release air). Push it so the round part of the green valve is entirely on the inside of the pillow. Once it pops back in there, it should work perfectly.