I have Figured out how to use hub link in Hubitate and put in the IP adress for my Smartthings hub, I do I tell my smartthings hub to link to my Hubitat hub?
The companion App is Link2Hub
Ok but how do i get it on my smart things hub
You don't with hub link. You need to try Hubconnect. Although for how much longer it will work is the question, as ST is dropping groovy sometime in the future.
Here is some documentation:
HubLink documentation sends you to the Send Hub Events documentation.. I've just saved you one click
Although, I of course, recommend HubConnect too..
HubConnect is focused on sending Events to another hub, ST or Hubitat, while the Send Hub Events path was built to ease migration to Hubitat. It doesn't handle a large set of Attributes like HubConnect can.