I'd like to use this one on my Canon T3. What kind of adaptor would you guys recommend?
That is not a lens but an accessory optic. You cannot simply buy any lens or optics and expect it to be compatible.
For a real fisheye lens, you would need one with an EF or EF-S lens mount. For an accessory optic like the one shown in your question, you need to make sure the threads match between it and your lens.
In the case where the two parts do not match, an adapter is needed butthey only really work one way, adapting a larger element to a smaller one. IIRC correctly, the Canon EF-S 18-55mm IS lens has a 58mm thread. If the accessory optics has thread larger than 58mm, say 67mm, you need a step-up ring from 58mm to 67mm.
If the accessory optic has a smaller thread, say 49mm, then they would attach using a step-down ring. When you take a photo, you will see the inside of the optics though! That would pretty much be useless.
The attachment is intended to be used in front of the lens, and it has a male thread at its rear end, to be connected to the female thread of your lens. Either this one will fit directly, or, if not, it will need an adapter ring for the two threads, the rear thread of the attachment and the filter thread of your lens. They are both supposed to be found either on the lens and attachments themselves, or in information material. You can easily find this information for your lens if you look for its full specifications. For the attachment, there should be information of its thread adjoined.
It is not only a wide angle attachment, but it can also be disassembled so that only the rear part is used, for close-up photography.
In either case, the image quality will suffer severely from an attachment of this kind.