As you have a physical remote, I think it is safe to assume that you have a Slingbox 500; for this model, you do need the physical remote to set the unit back up via Wi-Fi through the On-Screen User Interface. You can replace this remote by purchasing this from our accessories page, which I have linked below:
However, you can also set this model up via a Mac/PC, so long as you have this plugged in via Ethernet. If you do proceed this way, the Slingbox will have to stay connected by Ethernet until you find or replace your remote and adjust the settings again. I will link the setup article below as well, just in case:
I hope this helps!
Sling Media Technical Support