Join a program
Somebody running a program will have given you a ten-character code. Typing it shows you the terms. Nothing is enrolled until you pick a trial and say so.
Programs you run
A program is a question you are paying to have asked on ground you do not farm, and the terms you are offering in exchange.
Trials you have enrolled
Yours, and any belonging to a grower who has given your organization a full grant. Withdrawing takes effect from the moment you do it.