You have to email CPSloan with a request. I don't remember the email but Ill be getting 4x 600RTs from them to demo real soon.
Do you have to give them a credit card number?
No, you just need to be a CPS Gold/Platinum member. Most people register and pay with a CC for those, but I believe you can mail them a check or something similar.
I borrowed the 24mm TS-E and 100mm IS Macro, and haven't bought either yet. Probably buy one or the other eventually, but I'm in no hurry. It's pretty easy, just email them at the email address, say which lenses, when you'd like to receive them (but no guarantees), and eagerly await them
You don't specifically say "I will be wanting to buy this lens", especially because it's an evaluation
program. So even if you doubt you'll buy it, they want to give you the opportunity to shoot with it because you might just find you do want it.