Each manufacturer has a different way of wiping / resetting the tablet. I'd suggest trying to contact the manufacturer, but here are a couple of things to try.
Hold the power button down for 15 to 30 seconds. On some brands, that does a reset, but I don't know that it'll bypass the lock screen.
Try holding the power down button while pressing the power button. If that's doesn't do anything, try the power up + power. That might do a factory reset, which will wipe everything you've installed, but at least give you your tablet back.
meyerweb, the OP has probably gone, never to return, but Why oh Why, do people lock their screens with Passwords which they immediately forget or with apps which they can't use??