1. Find "Locking"
If required, click Advanced.
Click the top left icon.
2. Enter password
Highlight the field next to Change Code and key in a password of your own choice.
It's important to remember the password as you need to key it in if you want to change the settings later on.
3. Select lock settings
Click the box next to the required settings to select them.
When the box next to a setting is ticked (V), the setting is locked.
Click OK to close the window.