Where are the additional images?

I have uploaded some products with some additional images, using the native functions of zencart. I have the images numbered as instructed, and it all works fine. Now, if i need to edit some images, or add some or remove some, how do i go about it? Say i have my main image called IMAGE.jpg and additional IMAGE_01.jpg IMAGE_02.jpg and IMAGE_03.jpg. They are all installed correctly, but i want to remove IMAGE_01.jpg and add IMAGE_04.jpg without touching my main image. I cannot seem to find a way to do that without messing up everything else and having to start from scratch. Is there another way?

I cannot seem to find a way to do that without messing up everything else and having to start from scratch. Is there another way?
Just delete via FTP the images you no longer want

Do i have to go through the editing of the product description and such to add another image in the serie or can that be done directly from the FTP?

and add IMAGE_04.jpg without touching my main image

Do i have to go through the editing of the product description
Not if you do not change the main image