If you want to review your accounts login (session) history:
Click on your user avatar in the top navigation bar and select "Settings"
Click the "Password & authentication" tab in the "Security" group
Scroll to the "Sessions" section
Here you will find a list of all previous logins to your account.
If you see any suspicious logins, change your password immediately.
Revoking sessions
If you need to revoke a session for any reason:
Click on your user avatar in the top navigation bar and select "Settings"
Click the "Password & authentication" tab in the "Security" group
Scroll to the "Sessions" section
Click the session you wish to revoke
Click the "Revoke" button.