open image, then click on add filter, and pick textures
and where it says category and defaults to ALL, there is a button on the right on that which looks like a broken box with an arrow going inside thebox from the top left
click on that box and you will see the textures on the left window
and then click on Add Category - and call it whatever , something like daily textures or flypaper or French Kiss, click on it afterwards and click the right button that says IMPORT texture, and choose a directory, control A for all and enter and they will be added
as for the download/categories manager, I have no idea what he is talking about
hope that helps
