How to put on fisheye lens on a Nikon SLR?

I have a Nikon D3000.

I'm going to order these:
http://cgi.ebay.com/...415b709d25

Can those fit mine? I have a 18-55mm lens. How do you put them on? I'm pretty new to this. Do I twist it on or?

Added (1). Can that fisheye attachment lens fit my lens?

Added (2). Also, what's the different between the.40x and.25x? What do you call those(.40x, etc) anyway?

That add-on diopter screws into the filter threads of your 18-55 mm lens and that thread is 52 mm

But first you have to know that what you are buying is NOT a fisheye lens. If it were, you would 1) be removing your 18-55 mm lens and replacing it with the fisheye and 2) unless the field of view is 180 degrees or more, it can't be by definition a fisheye lens. A true fisheye will cost from just over $400 to about $1, 000, so you can see what you are buying is a compromise to say the least

That said, you will have a better chance of seeing a full 180 degrees if you buy a 0.25x fisheye adapter than the 0.40x. Just do the math.

It's an inexpensive attachment that screws on to the front of your 18-55mm kit lens. Your view will be darker and the quality won't be great, but it'll give you the beloved fisheye effect.