First of all, without your oven's exact model number it is difficult to get the right manual and precise instructions for it, however here is the main ONLINE SUPPORT page for what is hopefully a similar model:
And here is a direct link to the ONLINE USER'S MANUAL for that model:
To view the Support Page or the Owner's Manual with Operating Instructions just use your mouse to click on the link, which is the underlined and 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 or the contents of the Owner's Manual.
You may need ADOBE READER installed on your computer to read PDF documents.
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.
See page 22 of the ONLINE USER'S MANUAL for detailed instructions and illustrations on SETTING THE LOCKOUT FEATURE.
Basically you just press and hold the LOCK button for 3 seconds to either engage or disengage the lockout feature.
To clear off the F1 ERR code just press the CANCEL button.
If the problem persists, try shutting off the power supply circuit breaker for the oven at the house's main power panel box. Leave the breaker off for 5 minutes then switch it back on and try the oven again.
If this is not your model, just check your oven and let me know exactly what yours is and I will then provide additional information if necessary. Please comment back here to this page if you have any questions, have difficulty accessing the links, or just require further general assistance and I will respond as soon as I see it.
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Thank you very much and good luck.