When I first wanted to pull a single tile from a texture atlas in Unreal Engine 5, the idea seemed more complicated than it really was. A texture atlas is just one image divided into a grid, and UVs are the coordinates that decide which part of that image appears on a surface. Once you understand how those coordinates work, you can use a single material to show different tiles from the same sheet, which is especially handy for decals, sprites, and other reusable assets.
https://dev.epicgames.com/community/learning/tutorials/y9G8/unreal-engine-fortnite-ue5-texture-atlas-material-trick-you-ll-actually-use-tutorial