Receptacle replacement
Pigtails and Wire Nuts

Use short pieces of 12 AWG wire as pigtails. If you have any 12 AWG NM (aka Romex) lying around, you can take a black and white wire out of that. Connect all the hots together with a black pigtail using a wire nut and connect the other end of the pigtail to a screw on the new receptacle. Same for all the neutrals with a white pigtail. All grounds should be together as well, using a bare or green wire.