Create Local Copy of Existing WP Site

I just inherited a WP site and I need to create a local copy of it for testing and development. I’ve read some tutorials on the process and I’ve downloaded all of the files. I’m using MAMP and Sequel Pro on a Mac.

Do I need to download the database?

I tried exporting the content from the site. It gave me an XML file, which I imported on the local site, but it returned a bunch of errors and failed to import a lot of the content.