Starting iMac again from the very start?

Hi

I've got myself a new iMac and when I started it up I was in such a rush to have a play on it I skipped the inital transfer of files option from my old macbook.

I've subsequently copied all that old user over but now I have 2 users on the new iMac, is there any way to merge these or do I have to do a clean reset and wipe the iMac?

If the later do I just do that using Disk Utility and if so what happens to the OS as there are no OS disks (or cd drive obviously) in the new iMac?

My old macbook was running the old OS as well so once I do the clear reset / wipe and correctly migrate all my old data over at the start will the iMac put that all on the new OS?

Thanks in advance.

Iain.