Tailscale Unifi Site to Site

Hello there, I am looking to setup a site to site with tailscale on a udm pro and a udr7.
What I need to do is the udm pro is in the united states and the udr7 is out of country but I need to connect devices to the udr7 and have them on the subnet of the udm pro in the united states.
I am struggling with getting this running and a bit lost on this. I have the devices running tailscale via this GitHub - SierraSoftworks/tailscale-udm: Run Tailscale on your Unifi Dream Machine But I am stuck on getting a conection to the udm pro so I can have its subnet.
Any help pointer would be great
Thanks