So your wifi is 192.168.1.1, and I will assume that your other LAN is something other than 192.168.1.x. Just to Start/Settings/Network Connections, right click on the MiFi adapter, select properties, highlight Internet Protocol in the white box area and click properties, then check "use the following IP address." Type in an IP address like 192.168.1.2, subnet mask 255.255.255.0, and gateway 192.168.1.1.
I can't give you specific instructions for the MiFi, but you will want to configure it for the client computer being 192.168.1.2 through a static address or reserved dynamic address.