In short from a Studio or Robot installation that has internet access you:
Use the regutil.exe to activate a license.
Use the regutil.exe to export the license
Upload the exported license to Orchestrator on the License page
Profit
There are also details in the regutil documentation if you don’t have a machine that can activate a license online, to manually use the http://support.uipath.com/activation portal after generating a certificate with regutil.
More in-depth details are in the Orchestrator and Robot guides.