You could not get a New Products sidebox from installing Categories Dressing - there must have been something else you did at the same time to bring that up. You have it sorted now, anyway...
I see you have installed both the base Cat Dressing and the ch_categories option. You do not need or want both of them for your situation. Unless you want the expanded categories, you should delete the ch_categories files. There is not a one-click method for this; you will need to find and delete each of those files (and only those). If you might want that option, you could just turn off the chcategories sidebox in Tools > Layout Boxes Controller, and rename stylesheet_chcategories_dressing.css to stylesheet_chcategories_dressing.bak.
Read the instructions for creating category groups. You will want to make two groups, one starting with the first category in Designs and one starting with the first category in Clipart. Make new defines in categories_dressing_defines.php like this
define ('CAT_BOX_HEADING_33','1|0|||Designs|1');//new list - text heading - style 1
define ('CAT_BOX_HEADING_77','1|0|||Clipart|1');//new list - text heading - style 1
``` replacing 33 and 77 with the ids of the first categories in Designs and Clipart.
You currently have all of your categories arranged alphabetically, presumably with Design and Clipart intermixed. You will need to go into Catalog > Categories/Products and assign a sort order to each category. Make all of the Design categories lower numbers than the Clipart categories, and number them with gaps like 10, 20, 30, 40 so you can easily insert new categories later.
Once you have your groups, read the styling section of the readme, then post back and ask how to get the boxes.