Evernote files are usually exported in a extension called .enex. Right now we are not supporting .enex import, but there are a few options. First, you need to export the .enex file from Evernote, here you can find the official documentation for this.
Convert .enex to markdown files with a 3rd party tool.
There are a handful of 3rd party options that let you convert .enex files to markdown files. One of these tools is https://github.com/akosbalasko/yarle. It generally works well with simple documents.
Migrate .enex with your existing note-taking app
If you are already using a note-taking app that supports .enex import and Markdown / TextBundle export, you can use that app as a middle step.