The easiest way is using the Desktop CLient. you reorganize folder just like you normally would on your machine. The client just syncs those changes. But if you are working off the web interface, theres a rectangle icon on the left of the file and you can select each or bunch. You can use the left shift key to do multiple selection, then just hit the trash icon then delete.
You need to hover over the file icon with your mouse. When the cursor hits the line, the triangle shows up. When the triangles shows up, you will notice a triangle next to the 'name' at the very top left hand side of the list, then you are able to click it to hightlight all of folders