Pretty much what @xeithe said. Also update your computer's antivirus, and don't click any weird links. (Trust me, my dad works with IT security, haha) That being said, having backups on a disconnected HD is a great thing to have in case anything happens to your computer at all.
It should be noted though that this virus' makeup is nothing special, there are millions like it out on the internet, and it doesn't stop at any country borders (150+ countries, not just Britain and China were affected by Wannacry). What made this particular strain so successful was the laziness of companies and private users who didn't download updates since March, and it makes for a bona fide scandal when the NSA decided to keep this security issue to themselves for spying reasons instead of reporting it to Microsoft.
What I'm trying to say is always update your PC and antivirus, because this shit is always out there on the internet, and Microsoft and antivirus companies are constantly updating their software in a neverending race with criminals. Organized crime is turning to ransomware instead because it involves at least as much money as oldschool robberies, but with a considerably smaller risk. So. Yeah. Always update.
