If you carefully cut the dc jack off, with the blue brick switch off!, there will be a red and black wire. Connect those to your battery screw terminal on the board.
Thank you. I’ve managed to get power to the board.
I bought this switch. I was told it should work with the battery I have. It has four connectors. I should solder the ground from the soundboard to the yellow connector and the positive to the clear? On the opposite end do the same thing and those cables go to the battery. I know this is simple stuff, but I appreciate the help.