Hi niceguy001
1. For client VMs in "Prefix" you need provide common prefix of VMs names which are involved. For Example, if there are 5 client VMs with names "test1", "test2", "test3", "test4" and "test5" then you need to provide "test" in Prefix.
2. AD users will be created after you start a run and its not required to entitle desktop pool manually because viewplanner will do it automatically during run. Just make sure Identity Server is getting "Tested Successfully" and if it is failing then try again after setting up SSL certificate in Active Directory. Use this link(https://social.technet.microsoft.com/wiki/contents/articles/2980.ldap-over-ssl-ldaps-certificate.aspx) for instructions to set up SSL in Active Directory in case required.