WiFi Thermostat - C Wire
Yes, the terminal labeled C on the transformer is where you want to connect the C wire to the thermostat.  However, you'll want to make sure that the transformer is large enough to also supply power to the thermostat.  If the thermostat draws too much power, you could end up burning out your transformer.  It might also be a good idea to put an appropriately sized fuse in line with the R wire.