RPM upgrades are currently released twice a year. The latest version of RPM is 6.0.5. You can see the version you currently have installed on the System Info screen under the Help menu in RPM. The type of database you have will also be shown on that screen. Use the correct upgrade link depending on whether you have an Access or a SQL Server database.
If you have an RPM Onsite license with an Access database, upgrade here.
If you have an RPM Onsite license with a SQL Server database, upgrade here.
If you are using RPM Cloud, upgrades will be installed for you.