What is an OPML file anyway?
Outline document written in OPML (Outline Processor Markup Language); used to exchange lists of Web feeds (such as .RSS files) between Web feed aggregators
You can import a collection of Really Simple Syndication (RSS) feeds from an .opml file. This is a great way to use a collection of RSS Feeds from someone else or from an old computer that you’ve used to read RSS Feeds.
If you're a Feedly user, you can import your Feedly account by exporting your OPML and then uploading it into ContentApp.
If you go to https://feedly.com/i/opml you will be able to export your sources as an OPML file.