We currently have a beautiful 2yr male Jack Russell. We are wanting to add a female to our family & love the idea of breeding them.
I haven't owned a un-steralised female dog before & currently researching into it. Would anyone have any advise about looking after female dogs & preparing her for pregnancy?

Never bred dogs, but I have read that you need to give the pregnant females a high quality dog food that is balanced for puppies. Read the label and if it says good for pregnant dogs, then that's what you would feed her. The word is that you don't need to feed them any supplements like calcium or anything, if you feed them the correct food.
You DO need to get your vet to check the female's and male's health before you breed as they can pass on eye and joint and other problems. She needs to be in top health both physically and emotionally and make sure you know all of the peculiarities of Jack Russell pregnancies. I seem to remember that it's a difficult thing to do to make sure that you follow the breed standards. You may need to research more thatn I can tell you.
You also need to wait until she is fully grown to breed her and I think that is 1yr, but I am not entirely sure about that....again, good thing to ask your vet.

You definitely need a specially formulated diet for pregnant bitches. Also, you need to make sure that your female is properly wormed.
You need to keep track of your female's breeding date so you can know when to expect certain things.
After about 35 days, the mother's caloric intake will need to be increased. She'll need about twice as much food when pregnant and about 3X as much when puppies are born and she is nursing.
I agree with deano that the best thing to do is consult your vet and find out all the information you need before undertaking. When done correctly, the whole experience can be fun and exciting, but it is a lot of work. Hope this helps some.