K4003 2x30w amplifier running sub woofer

hi,
i wanted to know how i could power my sub woofer on both right and left outputs

Please elaborate, as we do not quite understand your question.

i want to run 1 sub woofer of both channels, so to acieve both left and right signals to one speaker rather than 1 speaker left 1 right.

You cannot parallel speaker outputs.
Possible solution: get a dual coil speaker.