How do I connect one netgear router A to netgear router B?...router b is a newer router that's connected Tina comcast modem. In my room, my computer and and router A are connected by an Ethernet cable. What I want to do is to get internet access by connecting router A wirelessly to router B.
Most basic routers can only be configured as a WAP (wireless access point), something to which wireless clients connect. In order to have your router function similarly, it would need to support that reconfiguration. As I said, most basic routers don't.
Since both routers are from the same manufacturer, it might be possible to bridge them over WDS. I believe Netgear refers to this as a repeater configuration. In this case, you identify the wireless MAC address of each router to the other so they can find each other to form the bridge.
If WDS is either not available or incompatible, you might be able to install dd-wrt on one of the Netgear routers and reconfigure it as a wireless client/repeater. Just depends on the make, model, and hardware version of the router.
If all those options fail, your only remaining option (at least in terms of wireless) is buying a wireless ethernet bridge. Most savvy buyers would buy a dd-wrt compatible router and (as I described above) configure it as a client/repeater bridge. Or else buy a standalone, dedicated device.