Copy the rudder-multiserver-setup directory to you instance.
Run rudder-relay-top.sh as root, replace <rudder-web> with the hostname of the rudder-web instance:
cd rudder-multiserver-setup ./rudder-relay-top.sh <rudder-web>
Take note of the UUID. If you need it later read, it is in the file /opt/rudder/etc/uuid.hive