It has to be the alien species, that's all. It can't be a Vulcan, Human, etc. Also make sure the you extract the zip file to STO's screenshot folder. The images need to be on there
Just to confirm, you put the images in STO's screenshot folder, correct? They cannot be anywhere else, they must be in that specific folder.
After that's done, go to any tailor. Click on one of your bridge officers who is the Alien species (not any other species). Click Modify, as if you were editing their uniform. Click the Load Outfit button. Now, assuming the images are in the screenshot folder (they cannot be in a sub-folder or any other location) the game will list all of them. Then you can click one and click the Load button.