This page shows you how to run the Cfx.re platform server (also often named 'FXServer') on Windows, Linux, txAdmin and there's even a ZAP-Hosting guide! They can all be found down below under Available guides.
If you haven't done so yet, register a free license key on the Cfx.re Keymaster.
When asked for an IP, the IP should be the public IP on which you're going to first use the key. Afterwards, the key can be used for a single server instance on any IP.