Here is the achievement world by Itzz Sh0wt1m3 which will help you obtain all the achievements in the 1.1 Discovery update:
https://www.dropbox.com/sh/xf2ist5cbnvpa32/AABwd31e_ManKgHvQ...
For this one, just simply have the lead equipped and use it on a llama that prompts you to use it and then it should pop. If not, you can always spawn another llama because that is an item you have and just lead him.