Wgr614v10

> I use a Netgear wgr614v10 router. [...]

   An antique.

> [...] I bought a WiFi dual band extender [...]

   Maker?  Model number?  Connected/configured how?

> [...] everything says [...]

   Thanks for the helpful links.

> [...] When I go to my router admin page it only says enable said
> broadcast and doesn't offer 2g or 5g choices. [...]

   Visit http://netgear.com/support , put in your model number, and look
for Documentation.  Get some.  Read.  Look for "GHz".  The fact that you
can't find it would suggest that when the WGR614 was designed, there was
only one radio band for wireless networking (2.4GHz).

Knowing nothing about your (unspecified) "a WiFi dual band extender",
I can only guess, but perhaps it can't _extend_ a 5GHz signal when there
is no 5GHz signal to extend.

> [...] My tv is horrible because the signal is too weak. [...]

   Get a better router?  Move devices around?  Run an Ethernet cable to
your (unspecified) "My tv"?  Many things are possible.  But getting a
5GHz signal from a WGR614[vX] might not be one of them.