Hyperlinking Table of Contents to Chapters Epub

I built a book in Indesign specifically for output to Epub. I have each chapter or section as a separate Indesign file, which helps tell Indesign when to break to a new page when exporting as an Epub file. I would like my contents page to have hyperlinks to the other chapters (other Indesign files) but am having trouble figuring out how to do this. Looking for someone who has built a book this way and knows how to have the hyperlinks work after the Epub file is exported. I've tried adding them in by right clicking and adding a new hyperlink. Then tried choosing hyperlink to a page (but I think that only works in the same document) and also tried choosing hyperlink to a file but that did not work. Can this be done in Indesign before exporting as a Epub file or do I have to wait till after I export as an Epub and then use another program to add in the hyperlink? Any help would be appreciated.