Unfortunately on Chromebooks it's not possible to do a device wide install, this means Truple only runs on the profile that it's installed on. This isn't a limitation of Truple, but of Chrome OS. What you can do though, is limit your ability to access guest mode and other accounts.

In order to lockdown the chromebook, the chromebook needs to have a chromebook account owner account that the child or individual needing accountability does NOT have access to. The only way to switch the Chromebooks account owner, is by factory resetting the chromebook. The very first account that logs into the chromebook is established as the chromebooks owner. This owner account can then disable guest mode and limit the profiles (email addresses) that can login to the chromebook.

Powerwash (Factory reset) the device

1. Login to the Chromebook as the current account owner
2. Click on the clock in the bottom left corner, then click the gear (settings) icon
3. Click Advanced
4. Click Reset settings
5. Click Reset. WARNING, this next step will wipe out all data on your chromebook. Backup and save anything important.
6. Once you've backed everything up, restart the device.
7. Once reset, the first account to login to the chromebook will be the new owner. Work with your parent or other report recipient to find an account owner. Then login with that account on the chromebook to set it up as the chromebook owner.

Disabling Guest Mode and Other Profile Logins

1. Login to the Chromebook as the current account owner (from step #7 above)
2. Click the Clock → Gear icon
3. Click "Security and Privacy"
4. Click "manage other people"
5. Disable guest browsing.
6. Restrict sign in to the following users -> click Add user to add someone who hasn't already logged into the chromebook. Otherwise just toggle existing profiles on/off.