1.Pull bottom hose off rad
2.undo top hose to engine.
3.unscrew the cap on expansion bottle
4.blow down top hose until all coolant has come out of bottom of rad.
5.put all hoses back on.
6.start engine and fill with coolant/water..50/50 mix.leave cap off for now.
7.inside the car turn heater on hot full power.
8.whilst checking the coolant level in expansion bottle,rev engine at about 3000rpm until you get constant hot air from blower.
9.then switch off blower and check coolant level,top up to max if low and put cap on.
10.all this time engine is still running.now rev engine again at 3000rpm until you hear the fans cutting in.
11.then idle until you hear fans stop and rev again till fans cut in for a second time.
12.switch off engine and let it cool down(10 minutes)
13.finally top up coolant to max and your done.
As you have already checked that you have warm air in the car ,you will not have an air lock.
Good luck ..