Help! Setup for Rode Wireless go two for two people

Hi Guys. I bought the Wireless go 2 Dual Channel Bundle, which comes with the two transmitters and one receiver. How do I set it up so that it collects audio from both transmitters?? I am trying to use this with a friend for a podcast, but somehow only one of the transmitters is picking up audio. Do I have to buy another receiver for the second mic?