Using router (wgr614v9) as a switch

> [...] my main router. [...]

   Not a very detailed description of that device.

> What more do I need to do?

   You could configure your antique as a wireless access point.  Many
newer models have a convenient mode option to do that, but you'd need to
do it that hard way.  See, for example:

      https://community.netgear.com/t5/x/x/m-p/1463500

That's written for a Netgear C6300-as-WAP, but the steps are about the
same for any other router (any make/model) which lacks a one-step WAP
option.  Such as your antique.

   Note that that scheme leaves the WAN/Internet port on the
router-as-WAP unconnected.  (A WAP is all-LAN.  A model with the
one-step WAP option effectively reconfigures its WAN/Internet port as
another LAN port.  Without the one-step WAP option, you need to use only
the LAN ports.)