Pale Green Fingers and the Orange Tree

I got married just over a year ago and my siblings bought my husband and me this beautiful orange tree as a gift -

It is totally lovely, but I was really worried that they had obviously had a brief moment of madness, and forgotton how I can kill anything pot-based in a matter of months! The omens weren't good when it started to wilt and drop leaves a few weeks later.....

However, a move to the kitchen did wonders for our little tree and this is how it looks today -

A little bit sparser than the same time last year, but definately still alive, and even with a few new oranges! Though somehow they aren't as orange as they were the first time around.

While I am pretty pleased with myself for getting the orange tree this far, I am not really sure what to do next with it. I was wondering if there was anyone out there with some proper green fingers who could give me advice?

Do I prune? Do I never prune? When do I take the oranges off? Should I replant (this is something that has never gone well for me before)? What next????

All thoughts gratefully received!