You get this achievement by progressing through the games story.
In order for the goth kids to join your cause you have to look like them and have coffee and cigarettes. You can get the clothes from the homeless man who sits in front of the storage units. The coffee you need is sold at Tweek's parents coffee shop. In order to get the cigarettes you have to defeat the sixth graders who hang out in the alley beside Jimbo's store. Once you collect all the items head back to them and equip the goth kid outfit and they will give you a mission to prove you are not a conformist. Complete this and the achieve is yours.