I have a Verizon router/modem it my house, I have pulled
Cat5 to my garage 250 ft. away. The NVR will be in the garage. Will I be able to log into the NVR and see the cameras from my desktop which in the house since the wireless network in the house uses the same router. Thanks.
Yes, if all the items (NVR, desktop) are on the same LAN as the router, same subnet (like 192.168.1.XXX).
I'd make the IP in the NVR static, put that IP into your desktop's browser and you should be able to log into it from your desktop.
I'd either reserve that NVR IP in the router OR use an IP outside the router's DHCP pool (if router's DHCP pool is 192.168.1.49 to .99, use .200 to .253 for you NVR, cams, etc.).
The feature set of most routers of that type are limited so if no "reserve IP" function is available, not to worry; just assign a unique IP outside the router's DHCP pool as outlined above.