How do I install a stable version of Discourse on Docker locally?

Sorry @pfaffman, I’m quite new to this so my questions might be quite basic. I didn’t have any essential information on the current database so I didn’t think I needed to migrate it, after I

git checkout v2.6.6

I attempted to re-initalize it, so I got the errors above. How do I go about dropping and creating the database? I attempted the Notes from the guide: Beginners Guide to Install Discourse for Development using Docker but none of them worked for me