To unlock this achievement, you need to setup 8 outposts. First things first, you need to either move into Snyders Trucking Warehouse or the Fairfield Fairgrounds potential home sites.
To unlock potential homesites in State of Decay you can do either of the following:
Play the Main Game until you rescue Jacob Ritter, he will eventually heal his wounds then the two of you go house hunting. You can change your home then
or
In Breakdown, you can move in after moving into your first home.
To move in you need 12 People for the Main Game and 10 People for Breakdown.
Be sure to have 50 Materials.
Now you have moved into Snyders/Fairgrounds you need to setup outposts.
To set up an outpost, you'll need to go to any building and fully search it, once fully searched you press Down on the D-Pad to go to radio commands, you can select the "Establish Outpost" option for 50 Influence.
Now you've created your first outpost! Now you repeat the process 7 more times and the Achievement will pop.
(Be mindful that you can only use the "Establish Outpost" option a few times before you need to wait, so some patience is required here)
Happy Outposting! (is that a word?)