Check the Newer example that works with MonoGame 3.8.
TiledSharp MonoGame Example
This example shows how simple it is to draw a (TMX) map made with Tiled in MonoGame project.
Remember to add TileSharp to your projects References!
The (TMX) map file is not supposed to be build with content pipeline. Just add it to the project and set Copy if newer from the files properties.