Page 1 of Yamaha AV Amp - use of banana plugs??

Hi.

Just bought a whole load of banana plugs to connect my speakers to my Yamaha RXV596 (and some for my car sub-woofer)

Tried the car first. Disaster. The one for the car had to be spilt as the spread between the individual banana plugs is not correct. Probably a failing of my car sub-woofer.
Next (car) disaster. Prepared the caps by removing the blanking plugs; inserted the banana plugs and they just wiggle around, they are not gripped!

Before I start on the Yamaha I thought I`d check these two things.
First, the spread between the plugs is correct for the Yamaha - good.
Second, I can`t see how this connection is going to be made.
I know I`m meant to bust the blanking caps out of the Yamaha black and red binding post caps...but inside there is the threaded rod that those caps screw up and down on.
Where the hell is the "space for" and "gripping bit" that the banana plug is meant to slot into?

Cheers,