How do i introduce a new rabbit ?

I would recommend not putting them in the same cage. Pet stores tell people rabbit do good in pairs to sell more rabbits. Yes, they can bond, but a 5 year old female is not wanting to be social with a rabbit she doesn't know. They do best alone. You could put their cages next door to each other so they can visit but they won't be a threat to each other. Female rabbits can be just as territorial as males and can hurt each other pretty bad. Good luck!