To add to @austin’s comment, Obsidian works by instantiating folders on your computer as “vaults”. When you install and run Obsidian, you have to create a vault by pointing it at a folder of markdown files—such as the LYT kit you’ve found. Then, you access those files by opening Obsidian.
Note that specific questions about LYT should be directed to @nickmilo, perhaps via the existing threads on the forum. (E.g., LYT Kit (now downloadable!). LYT is not an official Obsidian thing, but one of several “getting started” kits that folks here have contributed to the community.