If your quad had a brushed motor in it then the brushes need to be broken in before putting a load on the motors by flying the quad.
To break in the motor(s) do the following.
Start with a fully charged battery
Set the Quad on a level surface
Pair the transmitter to the Quad
Push the throttle stick up till all the rotors start to spin
With all spinning turn the trim post down till the motors stop
Turn the trio pots up til the rotors again spin
Let the motors run this way at low power for 2 minutes. Stop and check for heat if any of the motors are excessively hot let them cool for 5 minutes then repeat above. Otherwise repeat above, excluding charging the battery.
Continue doing this until the rotors stop. Your brushes should now be seated and broken in.
Note: If you replace a motor you will want to so this to break in the new motor. It will have no ill effect on the other motors.