Below the boiler (I'm assuming here), there will be two silver valves attached to two pipes, one should be on the far right of the pipes that come down (a 22mm or 3/4" pipe), the next valve should be on the pipe next to it (15mm or1/2" pipe next to it), the flexible loop connects to those two valves.
There are different types of valves (dependant on make), some are quarter turn screw valves that turn with a screwdriver, others are plastic finger type turn valves.
Again dependant on the make, either only one of the valves will need turning to fill the system, or sometimes both valves need to be opened.
When filling, watch the pressure guage on the boiler, fill the boiler (when cold) to 1-1.5 bar, then turn the valve(s) off.
Carefree
July 2010