Posted: 22/10/2013 at 17:31
I would suggest a pot at least 50x50 cm, use a humus rich compost and soak the roots in water for an hour or two as soon as it arrives. Hopefully, your tree will come with some instructions. If not, try and contact the supplier and ask their advice.
According to the site below, you will need a second tree to pollinate or at least another apple tree in the near vicinity. Scroll down, the Braeburn is the third one down.