How do you test electrical sockets with these. I have accidentally disconeda ring main, and need to test which socket is at fault

What type do you have? Do you have the make and model number?

Do you have the instructions?

What does "disconeda ring main" mean?

There are some that you must actually touch a live terminal with the tip of the screwdriver to have the indicator light indicate power, and some that you only get close to power but do not need to touch live parts.