New computer - Upgrading Parallels from 9 to 11

I just set up my brand new iMac (Parallels not yet installed). On my old machine I have Parallels 9 running but with the new computer and OS X El Capitan I'd like to install the newest version of Parallels (11, I believe).

How am I supposed to do this? Do I need to download the old version 9 again and install it before I can apply the upgrade to 11? Or can I download and install the new version 11 right away?
I can't afford to have any Parallels downtime, at least not more than one or two hours. I assume once Parallels 11 installed I can just copy the Parallels 9 Windows petition file to the new computer and then load it in Parallels 11?

What's the best strategy?

One more question. I'm still using Windows XP. That is supported by Parallels 11, isn't it?

 

Please download and install Parallels Desktop 11 as per this article and then activate the Parallels Desktop 11 upgrade as per this article. And yes, you can use Windows XP on Parallels Desktop 11.