It's actually quite simple as it works by itself once you get it set up. You need to select the notes that will be sung, it is essentially telling the software which notes to snap to. Then bypass the others, this tells the software which notes to ignore. If you are unsure about what notes go with certain keys then you need not worry. In this instance, click the root note and the tonality (maj, min, etc) and Logic will highlight the notes of that scale for you

And if you don't know what a 'key' is or how to find out what key your song is in... then you probably shouldn't be recording music in the first place

I'm sorry if that sounds bitter, but I have had experiences with these types, and it's not fun.
But I'm sure you are fully aware of keys and their place in music. Then once you do that, you choose a response time. This tells the software how long to wait to affect the notes' fluctuations. Faster times will give you that AutoTune T-Pain effect. Slower times sound more natural and musical. The trick is to get it so you don't 'hear' it.