Getting your IPs from RIPE/ARIN etc. takes a lot of time and back and forth. Prepare at least for a month if you need to wait for someone else to transfer the IPs to you.

The obtained subnet can be advertised from your server(s) via goBGP or similar. There are 2 ways to do it dynamic or static BGP routing. You need to tell your server provider which one you want.

In dynamic setup you use your own AS# then you would setup BGP, and create a route object with ripe/arin for your ipv4 and ipv6 and specify the origin as your AS#. That would be dynamic routing as you could advertise or remove it from the provider on your own.

If you want it routed under our ASN of the server provider (more statically as they would have to add/remove it manually), they would create the route object for your ipv4 and ipv6 or you can, and specify Origin as ASN# of the provider, and they would simply route the ips to your server directly.