You need to understand that in laymans terms your pc has 2 IPs, one its Internet IP (WAN) [this may or maynot be static depends on your isp], the second is its local pc IP (LAN) [this looks to me to be dynamic however its quite simple to set a static one]

The IP you are requested to enter was the IP the echo showed you, this is telling the router which PC to send stuff to, when stuff is sent to the WAN ip, its "Routing" stuff from WAN to LAN ip's thus its name router.