How to renew iPhone development certificate

First, in the iPhone provisioning Portal, you'll see that your certificate is expired:

The only available option is to request for a new certificate. You hit Request certificate.

The next thing is to create a Certificate Signing Request (CSR). Two options are possible: if you kept the original CSR or create a new one from scratch. In my case, I kept the original CSR file from last year certificate request so I can upload it (and save time!).

Then you hit Submit at the bottom right of the form. After that, the request for the new certificate is pending:

Then an email comes from Apple asking you to approve the request:

Back to the iPhone Provisioning Portal, the request has to be approved:

After a few minutes, hit refresh on the browser to see the new status:

The new certificate needs to be downloaded and imported in your keychain. Simply double-click the downloaded certificate. It will import in the Keychain:

The last part which I'll summarize here is to update all the provisioning profiles that were associated (or signed with the old (and expired) certificate. This is done the the Provisioning portion of the iPhone Provisioning Portal, clicking Edit then Modify. After, you make sure the certificate is selected then you click Submit. This has to be done for every associated profiles. Once you get the new profiles, download them and import them in Xcode Organizer then sync with the development devices.