To upgrade your membership, you will need to fill out the form for that category of membership you are applying for.
The application instructions and form can be found here.
In addition, you should include a short note, to indicate that you
wish to upgrade your current membership.
For those upgrading from Associate to Full membership, please include details on the nature of the work done. It is important that the work experience should be in the psychological field. You will not need to pay the one-time processing fee again, but just the yearly membership fee if you are upgrading your membership.
Yearly membership fee payments can be made here: Renew / Upgrade Membership.