I’m not sure that understand your actions to install that home page, that’s why I’ll explain you how to import it and set as Home page step by step:
1) Go to Theme Options > Import/Export > scroll down to the section with Additional Pages import and find Home Flat in drop-down http://prntscr.com/cx4orv
2) Once you import the page go to Pages > All > find your Flat Home page and you may edit it.
3) If you want to make this page as Front page, go to Settings > Reading > and choose it http://prntscr.com/cx4ppr Save settings.
