My 2007 chevy impala blows warm air but the compressor is running and it is charged with freon. What can it be?

You have a clogged orfice tube filter. This filter is in the high side line of your A.C system. That is the small line somewhere along that line is a connection that you can take apart with a special tool that would separate the line. Once apart you will need a pair of needle nose pliers to reach inside line and remove filter.

Or you need to have the system recharged. Have it tested before tearing into anything.

need to fine AC charging port

The low pressure (add Freon here) port is against the firewall behind some hoses. Look for a metal line with a black cap. The high pressure port is down low near the air filter box.