You can’t delete all the data with one tap(it made for security reasons). If you are not premium subscriber or doesn’t use cloud sync just delete the app from your phone. You can intall it again from AppStore or Google Play.
If you’re using cloud sync you need to manually delete all accounts and its history. Enable account editing mode by holding any icon for several seconds, or tap the Edit button at the bottom of side-menu. Then by tapping Cross button you can delete every account. To delete all operations for each account – choose Delete All Transaction in next dialog. When you delete all accounts and its transactions – you delete all the data. The same goes with income or spending categories.
If after these actions you still do have some date in statistics – please, mail us at firstname.lastname@example.org and specify your CoinKeeper’s account email address.