Don't be afraid to put a little bit of force to rotate it (it's solid).
It fits in the hole like the key in a lock, and turns in a similar way.
I have to disagree with Didier: I think you should try to get it fitted. It ensures that the filament has a more gentle bend radius, hopefully reducing feeder problems.
I just feel like it's one more point of friction. And you're pulling the material in the opposite direction of the feeder only to then pull it back again. Personally I've never used it (my printer didn't even come with one as it was a very very early one).
My filament goes around filament guide, below the power cord (in fact, below another printed filament guide that protects the power cord), and then up to the pulleys on geeks variant of Robert's feeder. I feel that the large loop ensures that the filament is entering the feeder in more or less a straight line, which probably helps to reduce friction.
I also recommend not using the filament guide. It adds a lot of friction, as evidenced by the deep grooves that get worn in the underside of it, when it's been used a while (we see this on every printer that comes in for repair with a filament guide fitted). Not only is that adding friction, it means that you are getting ABS dust stuck to your filament and carried up into the nozzle where it can potentially cause problems.
If you do want to use it, you can make it easier to insert by filing a small chamfer on the inside of the tab, as shown below.
I forgot to mention the filament duster that I also have, just below the feeder.
Wouldn't the US distributor be the better option for support? I'm afraid I don't know their contact details. Didn't you buy the printer from them?