New to lightsail, domainname

Hi!

I put up an wordpress multisite lightsail instance with an static ip, and configured my external dns-service to link my domain to my new server, but when I go to my site using my domainname the addressbar in my browser changes to http://xx.xx.xxx.xx.xip.io/wp-signup.php?new=www.yyyyyy.yy.

Sorry, I'm new to this, but I would like to see only my domainname in the addressbar, and not the servers IP...