The alarm means the freezer is not getting cold enough. Just turning it off will mean you have a freezer that isn't cold enough and no way of knowing.
You need to find out WHY the alarm is going.
You didn't say what the make and model are, so we can't look for the manual, have a read and suggest maybe defrosting, checking any internal circulation fan, making sure that nothing in the freezer is obstructing an internal fan, making sure any air diverter flaps are moving OK, etc., etc.
Post again here (and maybe any other forums you can find like diynot etc) BUT mentioning the make and model.