You need to purge the air in the system when refilling, usually removing one of the heater hose will do that.
When engine is cold remove heater hose at the firewall or if it has a by-pass valve(4 hoses on a valve) remove a hose there, set heat setting in side cab to HOT.
Remove rad cap and fill rad until fluid is coming out heater hoses.
Reconnect hose leave rad cap off and start engine.
Let engine idle for 10 minutes, top up rad if level drops.
Heater should start blowing warm after 5 minutes
Watch rad opening for signs of bubbles, there should be none after 2 or 3 minutes, if there are bubbles then you could have a head gasket issue.
If you get sudden "boil over" in the first 10 minutes, then you do have a head gasket issue.
If rad level is stable, heater is hot and no bubbles then put on rad cap and test drive.