12fx mono out to subwoofer setup

i have the 12fx mixer using the mono out to a sub. If i’ve got a line in from the bass drum mic how do i route to the mono out? also, if i have a line in from a bass how to i make sure we’re getting a combo of the mono out and the tops?

any insight would be greatly appreciated.

tks

The mono out is a sum of the main left right outputs.

For your sub out you want to use the aux 3 output, then you can
control the send levels to the sub from the needed channels.