C3700 how to put into bridge mode

> C3700 [...]

   C3700[v1] or C3700v2? Look for "Model" on the product label.

> I log into the routers page and can find nothing about bridge mode.
> [...]

   Searching the User Manual might be easier and more effective than
searching the unit's management web site.

> Do I unclick the wireless gateway box? Will that do it?

   You can if you want to, but no.  A wireless router without radios is
still a router.

   Visit http://netgear.com/support , put in your (actual) model number,
and look for Documentation.  Get the User Manual. Read.  Look for a
topic like "Cable Your Modem Router to a Router or Gateway" or "Change
the Router Mode".  Or "bridge".