I have a Pontiac 2006 Grand Prix. My boyfriend changed the radiator a couple months ago. He just replaced the thermostat. Our car is getting hot to the max and cold air is blowing out of heater?

I believe he did.

The heater not getting warm is an indication of a air pocket, which would mean that just one heater hose is getting warm, the other one would be cool.

What's the best way to get the air pocket out?

I do believe there is a bleeder at the thermostat housing, not sure, and or leave the filler cap off while warming up, once coolant level drops from thermostat opening add coolant as necessary until full. But don't get your hopes up, those are aluminum heads on there and once they get hot, they warp, causing the head gasket to loose its seal. You could verify this first by doing a compression test on the cylinders, you find one or two low cylinders, head gasket would be blown.

OK thanks I really hope it's not the head gasket ugh

For now just focus on getting the cooling system properly filled. Getting all the air out can be a challenge. As well as using the bleeder valve I've heard that filling it with it parked facing uphill will help. A shop with the proper vacuum equipment to draw the air out may be your last resort. Unless you really cooked it when it overheated the engine is likely fine.