You will be able to transfer it by simply logging into the same App Store account that you made the purchase with. Once logged in with the same Apple ID, you can go into the App Store and select "purchased" to view your purchased items/applications. You can install the SlingPlayer for iPad on up to ten devices with a single purchase, so if it isn't showing up correctly you may want to contact Apple for further inquiry into the situation.
Hope this helps!
The Sling Media Moderation Team