regarding candy cc217 tumble dryer-there is 2 blue wires going to push on power switch how do I know which one of them is the live one

You use a voltage tester or a VOM. Never heard of such a dryer, where are you located?

On a switch it does not matter which wire you attach. As long as you know where the two wires go then attach one to each connection and you are done. The same principle applies to safeties.