I highly suggest you to use this method only when your device got frozen. The following steps are for the devices with the removable battery.
Your device is in turned off state now and you can turn it on whenever you want.
If have a non-removable battery device, then you need to use a combination of hardware buttons to force shutdown your device.
But, the key combination differs among Android devices.
So, I suggest you to try the following two key combinations:
Hopefully, any of the above combinations may work on your device.
If not, please refer to the user manual of your device or just do a Google search like this: (force shutdown device model).