Not sure if this is for your exact model but here is a link to an Online User's Manual for one similar:
http://www.kitchenaid.com/assets/pdfs/product/ZUSECARE/KECC508RPS_Use%20and%20Care_EN.pdf
Just click on the link (underlined and highlighted text) with your mouse and a new browser window will automatically open to show you the information in the manual.
On page 7, it reads as follows:
To Lock Cooktop: Touch and hold the CONTROL LOCK/
ALL OFF keypad for 5 seconds. After 5 seconds, CONTROL
LOCK will glow red, indicating that the cooktop touch controls
are in the lockout position.
To Unlock Cooktop: Touch and hold the CONTROL LOCK/
ALL OFF keypad for 5 seconds.
If you have any questions or require further assistance just comment back to this page and I will endeavour to help.
Good luck and please click on the 4 Thumbs Up rating icon if this was at all helpful.
Thank you very much.
Joe.