Rabbits need a tattoo in the left ear to be shown. Usually the breeder will put the tattoo in before they sell a rabbit. Some breeders don't have a tattooer, so may ask another breeder to help them.
The pedigree should have an ear number listed. This should match the tattoo in the rabbits ear. While you can breed rabbits who are not tattooed if you have the correct pedigree, it can be harder to keep records strait.
Tattoos are a way to identify each rabbit. Since breeders to tend to have many rabbits of the same breed and colour, it can be tricky to tell one rabbit from another. While cage tags are useful, if rabbits get out it can be hard to tell.
If you do not have the stuff to tattoo your rabbits, ask a breeder in your area if they will help you. There are 2 methods to tattoo, a clamp and a pen, so decide which one you would prefer to use and find someone who uses that one. Shows are a good place to find someone as there are lots of breeders in one place. You may want to find someone first so you know there is someone there who will do it. Have the tattoo numbers you want ready.