Can anyone explain this idiom into detail?
It means to elevate something to the next higher level, or the next extreme.
If you're playing your stereo and someone says "crank it up a notch," you'll turn the volume up a bit.
If you're at a party and all that is available for refreshments is soft drinks (Coca-Cola, etc), someone might bring out a bottle of spirits and say "let's crank this party up a notch!"
You might be eating roast beef for dinner, and I'll offer you some horseradish, saying "Add some of this to your beef, and crank your meal up a notch."