somebody please help -charging issues

I have a new alternator and battery and it still wont charge.My batt reads 12.40v with my multimeter and only about 10.5v on the guage.After starting it the batt still reads the same.hasta

Appears your alternator is not working. Check the wiring going from the ignition sw to the alt. The regulator (built into the alternator), needs input voltage, from the battery, to the alternator, via the ignition circuit.
You need to get an electrical diagram to determine the exact path, so you can verify voltage on the correct alternator jack.

Depends on the year of your rig. My regulator is in the ECM. 94 XJ.