Coil spring for garden gate - help please

[isnibs]

I bought a coiled spring gismo at B&Q to put on to a garden gate so it will swing closed. (kids come into the garden for balls etc but don't always shut the gate afterwards). No instructions in the pack just the coiled spring with parts either end to screw onto gate and post -4 screws in pack, 2 for each end .Also, I metal rod and 2 other small metal 'plugs' which don't seem to fit anywhere - what do they do and where do they go? How do I fit this to the gate please so it'll close.
I thought it was going to be a doddle to do until I opened the pack! TIA for any help.

[Clanad]

Like this one? http://uktv.co.uk/gardens/stepbystep/aid/2632
(Watch the video... Best of luck!)

[isnibs]

Clanad, that's the very one! Thank you for the link - and the video, I'll be giving it a go today. Fingers crossed.