What you bought is called a close-up lens or perhaps a supplemental lens. The close-up lens is a cousin of the lenses used in reading eyeglasses. When you mount such a lens, it changes the minimum distance, camera-to-subject. Now many will tell you that that’s not the way to go because they degrade the quality of the resulting image. I tell you that in most cases they work just fine, you will hardly notice any hindering.
Photo-grade close-up lenses are constructed using two lenses mounted together. This tried and true method mitigates an aberration called chromatic. Chromatic aberration shows itself as a rainbow fringe around the edges of objects in your image.
The power of a close-up is labeled as +1 or +2 or +3 etc. Sometimes they are called 2X or 3X or 4X etc.
The value as labeled uses a language common to an optician. A +1 has a focal length of 1000mm. When mounted on your camera, and your camera is focused on infinity ∞, objects 1000mm from the front of your camera will come to focus (about 1 yard).
Mount a +2 and now you start at 500mm = 20 inches. Mount a +3 and you start at 333mm = 13 inches. Mount a +4 = 250mm = 10 inches. Mount a +5 = 200mm = inches. Mount a +6 = 166mm = 6 ½ inches.
Because camera close-up lenses are simply refined reading glass lenses, you can go to the drugstore and at the reading glass display, hand-hold any of the spectacles before your camera lens. What you see is what you would get, as to magnification. Remember, photo grade lenses are what you want. In a pinch, I have used store bought lenses from the drugstore, and this worked out OK.