Typically, the wrench would go into a female shaft in the center of the bottom of the disposer. Try using a mirror. Not an expert, but I have never seen a disposer with a bottom cover.
Once you find it, and clear the jam, if it still will not turn on, look for a typically red reset button also on the bottom.
I finally gave up and called a plumber. I really wanted to fix this myself. In another house we used the wrench
and things went smoothly. I read quite a bit online. I did use a mirror, flashlight, and my phone camera.
I did find the reset button but it stayed in. I could find no place for a wrench to go.
Thank you for your efforts.
The young plumber took off that bottom cap. No place for a wrench to go. He saw rust in the bottom of the disposal and thought the previous owner had stopped using it. This plumber concluded this was an old model.I don't know what the old guy did when he ran his new dishwasher. he sink would fill with water for me! I had to swish around a spatula in the disposal to get the water to empty. I hated that task!
The plumber did hear a hum when turned on. I am hard of hearing. Two hearing aides. I heard no hum at all.
He had to break into the very bottom and just saw the wires, no hole for any wrench.
So we now have a brand new machine. It was needed. Thank you again! christine