During the first or second month (it will depend on how many missions you are offered in the first month,) you will receive a council mission and be given the option of a normal mission or the DLC mission. Select the DLC mission and complete it.
The mission follows the standard ‘extract VIP’ formula. The new character Zhang, will take on the role of the civilian and will only have the hunker down ability. The map is very smaller and has only minimal enemies, mostly Sectoids and Thin Men. Just be careful towards the end of the mission as a Chryssalid will show up. Once Zhang reaches the Skyranger, the achievement will unlock.