How do I lock my desktop?

The printable version is no longer supported and may have rendering errors. Please update your browser bookmarks and please use the default browser print function instead.

This may be different in some desktop environments.
Right click on your launcher panel and select add, then choose lock screen. This adds a "lock screen" button to the panel.
You can also press CTRL+ALT+L or CTRL+ALT+DEL to lock your session, which one depends on the desktop environment.