In RStudio Server Pro 1.1+, Shiny Server Pro 1.5.6+, and RStudio Connect 1.5.4+, there is experimental support for floating licenses. These are explained in detail in this article, and while you are unlikely to need a floating license, it can be helpful to understand the differences between a floating license and a traditional license.
With floating licensing, professional RStudio product servers lease a license from a persistent micro-server. The micro-server manages the license itself, and leases on that license can be acquired and released by the RStudio product servers as needed.
With traditional licensing, professional RStudio product servers manage their own leases. You activate and deactivate the license directly on the server, with no need for a separate micro-server for licensing. For most customers, this is perfectly sufficient.
Floating and traditional licenses are activated differently, with different commands based on the target server. Note that both types of licenses can be activated in online or offline mode. Instructions are available via the links
These commands are run on the RStudio product server itself.
These commands are run on the license server host.
Once the license is activated on the floating license server, use the instructions in the admin guide to connect your RStudio product server to the floating license server.