I've attached the pic.
If you remove the throttle body you'll see the butterfly valve inside. thats the big thing with 2 'wings' that open and close when you pull on the accelerator cable.
The ISCV allows some air to bypass the butterfly valve when it is closed (at idle) so the engine can still get some air. how much air it lets through will affect how high or low the idle rpm is.
The easiest way to clean the ISCV is to remove the throttle body, then look for the hole that is just in front of the butterfly valve (airfilter side of valve). That hole is where the air enters the ISCV. Get a syringe with petrol and squirt it into that hole. Dirty petrol should then come out the hole behind the butterfly valve (engine side of valve).
Once the petrol is squirting through easily and cleanly you have successfully cleaned the ISCV.
Sometimes the ISCV will be closed or partially closed when you reomve the throttle body, when this happens you will find it very difficult to squirt the petrol through.
If that happens you need to remove the ISCV from the throttle body and clean it seperately. Thats not hard, but its more hassle than using a syringe to squirt petrol through.
the super quick and easy back street garage style fix it to use a can of wd40 with the little red straw stuck on to improve accuracy. with the engine running and the air intake pipe removed from the right hand side of the throttle body, you squirt wd40 into the hole for the ISCV. this is easy but i prefer not to do it because all the crap you dislodge from inside the iscv will enter the inlet manifold, and then the engine, and although it wont be enough to block valves or anything like that, as a rule of thumb i try to prevent dirt getting into the engine.