If they are currently running on the same version of code and in the same cluster you have 2 options.
The first is to do a manual upgrade to the latest GA release from the TAC website using the link victorfabian provided.
The second option is to use the automatic upgrade feature under the Maintenance tab. If the VC finds a more current version than the cluster is currently running it will ask you if you want to upgrade. If you click Ok it will automatically upgrade all IAPs in the cluster -- even mixed HW. Just keep in mind that the version on the TAC site is the latest release and the automatic upgrade version usually lags behind the TAC site by several months. For example, as of today the current GA version is v.4.1.1.0 where the version posted for cloud upgrades is v.4.0.0.7.