You need the filling loop, which looks like a large plastic key, probably white colour and has 2 'O' ring seals.
While turning this 'key' shape until it gets past the locking lugs then push it fully up. With this inserted fully into its hole, and then turned 90 degrees to lock it, you can now open the valve, it is a small scalloped grey plastic knob which you turn anti-clockwise (when looking from below), just like a tap works (only it is upside down). If the knob slips off, just push it back on. When reach desired pressure close the valve and remove the filling loop (key)
After filling let settle for say a day or two then bleed your upstairs radiators to let out the entrapped air.
There you go
Ozz, February 2013
