Installing and running Windows 10 on an external HDD

My MBP doesn't have a very large internal HDD, and Parallels (13.whatever-the-latest-version-is) and Windows 10 are eating up a fair chunk, so my intention is to buy an external drive and run it from that (if only I could afford an external SSD!). Is it possible to move the installation from the internal to the external, or would I have to reinstall everything...? A 'for dummies' guide would be appreciated...

Finally, what's the speed like, running it from an external drive? I don't play games that chuck the FPS around (I can't, MBPs aren't made for gaming!) but there are a few on Steam that I'd like to play (waiting for them to go on sale) which are Windows-only and would run on here.

Oh, and FINALLY, finally, what EHDD should I buy? I keep being told that LaCie makes the only Mac-compatible HDDs, but the cheapest I've found for a 4TB is £120, would really like summat with a bit more space if it could be found for a similar - or cheaper! - price (without sacrificing speed too much). Any suggestions...?

 

Hello SarahB3, Please follow the instructions from this link and check if it helps.