Sounds like you may have the wrong version of Lightroom. There is Lightroom and there is Lightroom Classic. If you have Lightroom 5 installed, then you do not have a catalog. This is a new application, that stores images and edits in the cloud. Lightroom does have a local library, but that is just a cache to speed things up. If you have an old catalog (with file extension .lrcat) then you need Lightroom Classic, not Lightroom 5.