I have 2 slingboxes at the same location.
Each of them will have a different IP address (if they are behind a router) and the IP will be a private address.
10.x.x.x or 192.168.x.x etc.
Also give each one it's own unique port like 5005 for one of them, and 5006 for the other.
Use those unique IP's & unique ports in your port forwarding rules on your home router.
It works great, both will show up in your "DIRECTORY" on your phone app or sling.com, and you can choose which one to connect to.