Then turn off the tablet and when you turn it back on choose the reset. If you are trying to reset it and keep your data on it, note that will not fix many issues. Especially if there is a virus, malware, etc., on the tablet. That won't resolve it and a "Hard Reset" would be needed, as it wipes the device.
A "Factory Reset" should also be able to be done from the "Settings" in the tablet itself. For a "Hard Reset" you can do the following...
NOTE: Doing this will clear 'all' the data on your tablet, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the device.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard...