Ok, that other poster's post helps if you had a third party (own RJ-45 WAN port router) and want to keep FIOS TV working.
Since you do not, moving along.
You need to setup a Static IP on/for the computer that you want to host on and then forward to it.
There appears to be two ways of doing that, but I am not sure of that.
I am sure of one way of doing it, so I will tell you how to do that it that way.
#1 In the router go to Advanced -> IP Address Distribution
#2 Make sure the DHCP Range does not occuy the whole subnet.
#3 If the DHCP Range occupies the while subnet, select for Network(Home/Office) the edit button under action that looks like a pencil/pen and then make the DHCP Range smaller.
For example if the router's LAN IP is 192.168.1.1 and the DHCP Range is 192.168.1.2-192.168.1.254, then you could make the Starting IP Address 192.168.1.100 (which would make the DHCP Range 192.168.1.100-192.168.1.254)
#4 Then on your computer that you want to host on/forward to, you make it's manual Static IP outside of the DHCP Range.
For example with the router at 192.168.1.1 and the DHCP Range 192.168.1.100-192.168.1.254, outside of the DHCP Range would be 192.168.1.6
Full Settings outside of the DHCP Range for example would be:
IP Address: 192.168.1.6
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.1.1
(At least one DNS Server required, but typically two) ex 126.96.36.199 and 188.8.131.52
The second way of setting a Static IP, appears to be go to Advanced -> IP Address Distribution -> Connection List. Then from the list, that looks like this UI
Select the Edit icon under Action.
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