MyBB Community Forums

I would like to have a registration box on my forum home page on the top right of the page similar to that in this forum: http://www.awesomestyles.com/mybb-themes...thatshabbo

How would I go about adding that on (is it some code I can copy from the demo theme?)

You indeed need a modification for that (so you should've posted this in the modifications forum).

You can look at mods.mybboard.net to find something that suits your needs.