If let's assume that the tablet you have there is an Android?...then you'd go into your settings which it's icon would more or less look like gears and a wrench......next, you'll see a list of options for settings. Scroll until you find Phone Settings something like, 'Sign In' or' Create Google account.' If you are already utilizing a handset previously owned, then this would also be the area to head to incase the prior owner/user didn't sign out.
If you have an Archos Android tablet, the sign in account in settings may or may not be associated with a Google Account, instead it may ask for 'Exchange' account credentials, or some other un-Google service.