If you are looking for certificate replacement for APs in the network, then please follow below steps 

1. Create an AP certificate .req file from Ruckus wireless controller, for the desired AP(s).
2. Reach out to support at https://support.ruckuswireless.com/contact-us and raise a support case.
3. Provide the .req file with any additional details you have.

Ruckus support will help you to provide AP certificate file(s) and same can be utilized for the AP certificate replacement.