Can you specify what board are you using?
Anyway... look at the attached picture (it is a rev. H/J mnats' board). You can have two cases:
1) you have an electronically debalanced input (with IC) -> simply connect pin 1,2,3 on the board to pin 1,2,3 of the input pot
2) you're using an input transformer -> connect pin 1* on the pcb to the pot's pin 1 (connect pin 2 and 3 as in the first case)
Hope this is helpful!
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