Right, they only hire employees. The OP understands the process of reporting the "in-store" activity but does not seem to know how to report the "other activity", at this company it is known as administrative time. For most of Crossmark's assignments, merchandisers need to order "parts" which are new graphics, graphic holders, perfume samples or anything needed for that assignment. When you call in your orders you call in your administrative time. You are asked, probably unofficially, to add your drivetime between stores to your next assignment. For example, you are given 45 minutes in the store to complete the assignment for client A. If you drove 15 minutes to get to that location, you actually only spend 30 minutes on that assignment; thereby paying for your drivetime. All other time including ordering, reading emails, talking on the phone with your Area Manager or whomever is reported to the helpdesk, which is the same desk you use to call in your orders. If you do not have orders to call in, you still call in your admin time.
All of the instructions are in the bundle of paperwork and the 4-6 hours worth of training videos that they provide and pay you to complete. If you didn't see them and you got paid for your training, well, a hidy hidy hoooo. I've never seen a $3 15 minute assignment for them myself; doesn't mean they don't exist but you can't get your drive-time in on that assignment so you would have to call in your drivetime.