Go to your Google Account page
Sign in if prompted
Open Security
Under Your devices, select Manage all devices
Review the devices listed
Select each device you want to remove
Click Sign out
Repeat for all devices
Change your Google Account password
Turn on 2-Step Verification
Review recent security activity
Remove any unknown devices or sessions
Revoke access for apps you do not recognize
Sign out of Gmail, Chrome, and other Google apps on each device if needed