You might be able to manually force the window up if it's slightly ajar and the regulator isn't completely seized, but this is risky and could cause damage to the motor, regulator, or window itself. You'd likely need to access the mechanism from inside the door panel, which is a process involving removing screws and potentially disconnecting electrical components. Even then, it's not a guaranteed success and could lead to injuries.
Your best bet is to either:
* Troubleshoot the electrical system: Check the fuse, wiring, and the window switch itself before assuming the motor is bad. A simple electrical problem is much easier to fix.
* Repair or replace the window regulator: This often involves purchasing a replacement regulator motor assembly and installing it. This requires some mechanical skill.
* Use a temporary fix (if the window is only slightly down): You might be able to use a piece of sturdy cardboard or similar material to wedge the window up and prevent further issues until you can make a repair. This is strictly a temporary solution.
Attempting to manually force the window up without understanding the mechanism is strongly discouraged. You're much better off diagnosing the problem or seeking professional help.