Lemongrass has various uses from culinary to medicinal. Most of the time we only use the white portion near the roots.

First trim off the root-end of the lemongrass,

then peel off outer layer of the lemon grass until you get to the fresh looking bits inside, trim off the green portion.

Using your knife, smash and flatten the lemongrass, this will break up the stems and release the essential oils in the lemongrass.