Images must be imported into Lightroom. When you go through the import process, when it has completed, you will be looking at the images of the previous import (the import that you just performed). This is normal. If you look at the different sections on the left hand side of the library module you will see that "Previous Import" is one of the sections. You will also note that there is another section called "Folders". If you choose that section you will be able to see the other folders that you have imported.
Thank you, this works.
And can you tell me how to delete files from catalog?
One way is to simply highlight the file that you want to delete and then press the delete key. You will be given the choice of removing it from the catalog or deleting it from disk.
Another method is to go through a batch of images and press X when the highlighted image is one thing you want To be deleted. After you have gone to the batch you can press Ctrl/Bkspc and you will be presented with all the images that you have marked. You all have the same option to either delete from the disk or to move from the catalog.