With your Slingbox disconnected from any power supply, you want to connect the coax source for your TV service (either from your wall or from your cable box) to the input port on your SB, and then a second coax cable from the output port on your SB to your TV. Then, it is recommended that you program your router to set a static IP address for the SB, using the MAC ID printed on the bottom of your SB. In most cases, the recommended static IP address is 192.168.1.254 (if the IP address for your router is 192.168.1.1), or 192.168.0.254 (if the IP address for your router is 192.168.0.1), etc. Then program your router to forward port 5001 (both the TCP and UDP protocols) to the static IP address you assigned to your SB. Then you want to connect an ethernet cable from the ethernet port on your SB to an ethernet port on your router. Only after doing all of these steps do you then want to connect the power cord for your Slingbox.
If you then reboot your router, it should find the SB on its network fine, and you can continue with the setup routine for your list of stations, simulated remote control for your TV or cable box, etc.
Report to the forum if you still have problems connecting, and any error messages that you receive.