Here are your parts
Parts for Magic Chef CTB2124ARW Refrigerator - AppliancePartsPros.com

Measure the temperature in the freezer.
It should be between 0 and 5 degrees F.

Also is the compressor on all the time except when the unit goes through a defrost cyc;le?

[COLOR="Blue"]Worse, I don't have thermometer.[/COLOR]
I would go and buy one for a couple bucks.
You need to know the temperature.
You know it is at or below 32 degrees F but how far below is important.

[COLOR="Blue"] Can you advise how to check?[/COLOR]
You can usually hear it but also should be able to feel it vibrating.
See section 1 in the parts.

Also check that the condenser/compressor fan is on when the compressor is on.

Check that the evaporator/freezer fan is running.

[COLOR="Blue"]However, I can't figure out if the condenser/compressor fan is on when the compressor is on.[/COLOR]
Not sure what the problem is.
If you pull the unit away from the wall and remove the rear cover you can check the compressor, the compressor and and the cleanliness of the condenser coils.

[COLOR="Blue"]If the evaporator fan is working and the freezer temp is 18 degrees does that mean the compressor is working?[/COLOR]
Yes but that is not the problem.
The unit is not cooling efficiently.
You have to find out why.
I think you will find that the compressor is running constantly except when it goes into a defrost cycle which should last about half an hour.

If the unit is cycling normally then it could be a control thermostat problem.

[COLOR="Blue"]Is there something that normally triggers the compressor fan so I can check that it's working?[/COLOR]
The Compressor fan, the compressor and the evaporator fan are likely wired in parallel so when one is on they all should be on.
The parts link I included earlier does have a wiring diagram.