Open up your Epic Games Launcher and click Library
From your Library view you need to click on the 3 dots to the right of ARK: Survival Evolved.
Once you have done this, it will open up a new menu. From the menu you need to click on the first option Go to Store Page.
Scrolling down ARK: Survival Store Page, you will come to a section with the heading of Add-Ons. In here you will see all of the free/paid for expansions/DLC’s and maps. Click on the GET button to download your choice.
After doing this, follow the onscreen instructions, and your Epic Games Launcher will start downloading the new content for you. Enjoy exploring your new map/s.