Matters allows you to upload your bibliography in BibTeX format.
In order to import your EndNote library into Matters, you need to convert it to BibTeX.
1. Select the citations you would like to export.
2. Select File -> Export
3. Under output style, "Select another style...", and then choose BibTeX.
4. Open the generated file using a text editor (Notepad, TextEdit), select all, and copy.
5. In Matters, at the bottom of the page, select "Import from reference management software" and paste into the textarea. Your citations are now imported!