How can we get the water pressure to rise on the guage?

We turned all the radiators off upstairs and drained a small amount of water of in the bathroom before extending the two pipes to the radiator. We are now trying to restart the central heating so we tunred all the radiators back on but the guage is showing 0. When we turn the usual valve - number 2 on the plan - nothing happnes but usually it goes up. What are we doing wrong?

Dolly
December 2009