Slow Internet Mac Yosemite Recovery Doom (MacBook Air, Early 2015)
It sounds like there is a problem with the USB installer. To confirm this, restart holding Option + R to return to Disk Utility, and verify you formatted the drive as "Mac OS X Extended (Journaled). 

If you have a working bootable usb, holding the "option" key should show you the Startup Manager menu: 



https://support.apple.com/en-us/HT204417

Here are a few tutorials on creating Bootable USB OS X installers: 

http://www.intowindows.com/how-to-create-mac-os-x-yosemite-bootable-usb-using-diskmaker-x/

How do I create a Mac bootable USB drive using Windows?

http://www.makarandmane.com/computer/tips-and-tricks/apple-mac-os-x/create-bootable-usb-mac-os-x-installer-from-windows/