second wordpress site to practice on

I run a WordPress site but I want to try and learn more about the coding aspects, I dont really want to start poking around on the site i currently have in case i break something and cant fix it. I want to get a second wordpress site just to practice code on, any idea how i actually go about this without it interfering with my current site?

The last time i tried to make a sub-domain it really messed up the main site and I had to pretty much remove the whole thing and start again, i really dont want to do that this time.