Setup XCSOURCE 2 player USB Encoder

[lambsarse]

Hello, I've finally seen the light and I'm migrating from MAME on the PC the RetroPie. I have it all setup in a old Jammer arcade machine with CRT Monitor. I've connected the origonal buttons and joysticks to a XCSOURCE 2 player USB Encoder, the same as this:

https://www.amazon.co.uk/gp/product/B01LAUYMQ6/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

I've setup the Player 1 controller, however I'm unsure on how I go about configuring the player 2 controls?

Can someone point me in the right direction?

Thanks

Jim