If you get access to CMOS Online through your institution (a university or corporation), the best way to link your PerfectIt account is to follow the usual instructions here. If that doesn't work, please write to the help desk at the Chicago Manual to request access to PerfectIt (email@example.com).
If you get access to CMOS Online through Editors Canada, the nature of the collaboration between The Chicago Manual and PerfectIt means we can’t offer The Chicago Manual of Style for PerfectIt with your Editors Canada login. As for other associations, members of Editors Canada need individual subscriptions to both products to use the style in PerfectIt. However, members do get a discount. Log in to Editors Canada to get 20% off new and renewing individual subscriptions to CMOS Online.