For litter box training you will need to main things.
Litter
Litter box
Litter:
There are many choices of litter for your rabbit. Cat brand litter, wood chips, shredded paper, hay. Cat litter has a clumping formula making clean up a breeze, but should be used with caution. If this litter is ingested it could cause harm. I would observe your rabbit closely so if you notice your rabbit start to nibble at try to switch to a different litter. Wood Chips are another possible choice. If you choose this choice you should only use aspen chips. Pine and cedar chips are known to cause certain respetory problems. The next choice is shredded paper. You can shred it yourself or use a similar product found in pet stores. This is normally okay if occasionally ingested in very low quantities and can be easy to get. The last option is hay. Some people do not like this litter. They feel they should not be relieving themselves in something they eat, but I feel I should acknowledge this method to those who may want to use this method. It is okay for them to ingest and you will
Litter Box:
You can find this at any local pet shops. They come in a multitude of sizes and shapes. Ones with one low side or corner are best especially for special needs or older rabbits. I like the ones that clip onto the side of the cage and have one lower side for them to hop in easily and two really high ones to keep the litter in the box.
This is simple on your part. Many rabbits this is second nature for. YOu should put the litter box in the corner where he or she goes the most. Then place a few soiled pieces of bedding and a few feces into the litter box. Once they are trained you should, though, always be as clean as possible. When you put your rabbit in the cage you should place it in the litter box and leave him alone. You should notice him start to use it. Remove soiled bedding daily, leaving a bit in the box until fully trained.