I am new to arduino and I would like to use the maxim 18b20 to read temperature then an led corresponding to the temperature read. I have no clue how to return the value and then use it another function. Please bear with me.

Is this a generic C programming question, or is it specific to the 18B20?
Have you got any code?

Start here


and then have a look at some LED lighting stuff. It's probably just a single line of code that puts a pin high once a value is exceeded, followed by an else put it low.