I use a ¼" round flat punch to push the center post and insulator out...
Then wire a 20g red wire to the underside of the center post (using helping hands helps make the job easier)...
Then wire a 20g black wire to the inside (or outside) wall of the underside of the connector. It helps to first scruff up the area to be soldered on the connector, then apply flux, then apply a dab of solder to the connector and to also tin (apply flux and solder) the bare wire end before soldering the wire to the connector...
Wait for the connector to cool, then using the flat punch push the insulator (wet it first with water or spit) back in, then insert the center pin.