I have bought a solpadeine tens machine to help with the pain left from shingles ?

unfortunately there are no instructions in the box and although i have looked it up on the internet i cannot find out how to use the machine - there is mode abc etc., and there is intensity 0-8 - we have tried them all but don't know what we should be doing really - has anyone used this machine? can anyone help at all? advice would be appreciated. thanking you.