Just bought my first stack.. some assistance needed.

[thedastardlydude]

I just bought a Laney GH50L head and Randall 4x12 cabinet.
I've never owned a stack before, only combo amps.
I was wondering what loudspeaker output I should select on the head to run into the cabinet. There are dedicated output jacks for 1*16ohm, 1*8ohm, 2*16 ohm, 2*8ohm, and 1*4ohm. I have no idea how to calculate this.
The cabinet has a mono 8ohm input and a 4ohm stereo.
Someone willing to help this stack newbie?

[Jag]

Use the mono 8ohm input on the cab and the 1*8ohm output on the head.