If you are being prompted to pay or do not have full access to the questions, it is likely that you have accidentally created a free trial account, instead of a full institutional account through the CMU Libraries.
Students need to create their accounts from within the CMU IP network (i.e. on-campus, ether in Mount Pleasant or Saginaw) by navigating to the following URL to ensure that they are associated with your institutional account: http://cmich.idm.oclc.org/login?url=https://www-usmle-easy-com.cmich.idm.oclc.org/institution
If you have already accidentally created a free trial account, please contact McGraw-Hill Customer Support at UserServices@mhprofessional.com. They will then upgrade your account from a free trial account to the CMU institutional account.