I am a starter with Ligthroom 6. I don't now the way how to copy or add met pictures from my Mac to the Lightroom library. When I open pictures in Ligtroom, I het the message: no pictures.
Please view some of the Online Tutorials for LR. Specifically the ones about Importing images into the LR Catalog. While your at it view others about the proper use of LR.
You could also buy a book. There are several of those as well.