‘how to lock widgets’ for ‘Firefox?

Hi! If you mean Firefox widgets, the antivirus is unlikely to be able to “lock” them in place directly. Could you tell me which widgets you are using and which antivirus software is interfering with them?

If the widgets are moving or disappearing, you can also try disabling the antivirus/browser extension temporarily to check whether it is causing the issue. Once we know which antivirus and widget you are using, we can suggest the appropriate Firefox settings.