Convert wireless signal into a wired connection

I have a Verizon Jetpack (mobile 4G hotspot).  It creates a wireless network, but the device has no Ethernet jack on it.  I'd like to use a VOIP phone over the Verizon network, but I first have to convert the wireless signal into a wired one (the handset requires a wired connection).  I also happen to have one of these devices lying around unused at the moment:

http://www.amazon.com/gp/product/B005EIH4DE/

In case you don't want to click on the link, it's an ASUS RT-N12/B Wireless-N 300 home router.  It supports DD-WRT, although it doesn't come with DD-WRT installed.  Can I use the ASUS device to convert the Verizon wireless signal into a wired one?  If so, how?

I'm not really a networking guy, so if someone can point me in the right direction, I'd appreciate it.

Thanks.