retrieving library for reinstalled iTunes

I Am running Windows 7 and purchased the new iPhone 7+. I ran into some complications and had to uninstall and reinstall iTunes to get the newest version. However, the only music that came back was my purchased music. I have a lot of music that I imported from CDs many years ago. I see all of it in a folder on my computer. How do I get that back to iTunes?

Thanks so much for any help!