Hi David,
The home button plugs into the [https://www.ifixit.com/Store/iPhone/iPhone-6-Plus-Home-Button-Link-Cable/IF269-014|home button link cable|new_window=true], which is a flat ribbon cable [https://www.ifixit.com/Guide/iPhone+6+Plus+Front+Panel+Replacement/29710#s70022|sandwiched between the back of the display and the shield plate|new_window=true].
If the part you purchased does not include a new home button link cable, you can [https://www.ifixit.com/Guide/iPhone+6+Plus+Front+Panel+Replacement/29710|use this guide|new_window=true] to transplant the cable from your old screen to your new one (assuming it is in good condition).
If you prefer, we also offer [https://www.ifixit.com/Store/iPhone/iPhone-6-Plus-LCD-Screen-and-Digitizer-Full-Assembly/IF269-000-3|replacement screens with the home button link cable preinstalled|new_window=true] to make your repair easier (they do cost a little more). If you bought your screen from iFixit and would like to return it and purchase the "full assembly" version, just [http://help.ifixit.com/article/136-email-support|call or email us here|new_window=true]. Hope this helps!