Are you not placing the wire thru the hole in the binding post ? As you unscrew the upper part of the binding post, you will find a hole thru the shaft.. Place the bare wire through the hole and tighten the nut back down.. Done deal..
This will also work for pin connectors..
The area you were trying to attach the wire to is for spade use.. (And/or the bridging strap)


LFE ! The rest is just details..