*HELP* I need help connecting to the internet

I really don't want to repeat something  but I'm having some wierd issues with my Modem and Router. My ISP is Xfinity.

Modem: Arris Surfboard sb6141

Router AC1750

I am currently connecting my modem to my computer. Internet is fine.

So to name a few things i've tried are

1. Connect the Modem to the Router via WAN

           a. Using the LAN ports to my Computer via Ethernet

Results in Access to the router but there is no internet connection via Ethernet or Wifi

           *Note: I believe I was able to access the router configuration

2. Connect the Modem to the Router via LAN port

           a. Using Alternate LAN port to my computer via Ethernet

Resulted in having access to the Wifi, however leaving my computer with no access.

          *Note: I believe that I was not able to access the router configuration.

3. Turning both the modem and router off

              a.  Connecting modem and router via Internet ports       

              b. Turning on Modem

              c. Turning on Router

              d. Connecting Router to computer via LAN port

Resulted in same results as in #2

I really am at a loss and I really need help.