For my Slingboxes, I found that I needed to be able to login to the router that each Slingbox is connected to, in order to set the Slingboxes to a static IP address in the local area network of that router. And since, for security reasons, I have set up my routers so that they can only be logged into from a computer within their local network, I had to be physically present at the location of each Slingbox/router combination -- with a computer (laptop was OK) -- when I need to set the static IP addresses and forward port 5001 on the router to that static IP address. Once I did all that, both Slingboxes have worked great and I can readily access both of them and view what they are slinging on my computers from any place in Internet Land.
Just how you set a static IP address for a device on your router, such as a Slingbox, and how you forward a port to that static IP address, depends on what make and model of router that you have -- the instructions can differ quite a bit from router to router. What is the make and model of your router? Then perhaps another Slingbox user can respond with a more exact answer to your question.