Training can't be assigned. They'll have to create an account for each user and then register/purchase the training under that account. They will then need to create another account for the next user.

Unfortunately, there isn't a way to assign training to multiple users from one account. As this is the case, you'll need to create (or ask them to create) an account for each user you wish to enroll in the training and then register that individual user for the course you want them to take.