First of all, thank you very much for choosing FIXYA today for your technical support needs.
Here is a direct link to the ONLINE USER'S MANUAL for that model:
To view the Owner's Manual with Operating Instructions just use your mouse to click on the link, which is the underlined and blue highlighted text just above.
This will open a new web browser page automatically for you and allow you to view the information at the website indicated and the contents of the Owner's Manual.
You may need ADOBE READER installed on your computer to read PDF documents, although many computers already have this type of utility pre-installed.
You can download this free at WWW.ADOBE.COM
Click on the DOWNLOAD ADOBE READER button on right side of the ADOBE home page when you get there, then follow the onscreen instructions to install the software on your computer.
See page 10 of the manual for detailed instructions and illustrations on how to operate the CHILD LOCK feature.
Basically you just push the START button 3 times in a row TO ENABLE the child lock.
And press the STOP / RESET button 3 times in a row TO DISABLE that feature.
I truly hope that was helpful to you.
Some newer models require you to push those same buttons 4 times in a row instead in order to operate that feature so you can try that as well.
Good luck and take care.