To set up an app lock on your device, you can follow these general steps:

1. Go to the settings of your device.
2. Look for the "Security" or "Privacy" section.
3. Find the option for "App Lock" or "App Locker".
4. Enable the app lock feature.
5. Select the apps that you want to lock by setting a password, PIN, pattern, or fingerprint.
6. Customize any additional settings, such as timeout duration or lock method.
7. Save your settings and exit the menu.

Please note that the specific steps y vary depending on the device and operating system you are using.