Can I download Fedora to a flash drive to install via USB port
 

I have an extra system with no OS on it , I want to install Fedora on it , have no cd-rom on it but does have USB ports , can I download the OS to a flash drive from one active system and install the download to the empty system with Fedora download successfully

Fedora provides a disk image to format a USB device as installation boot media, and once the installer starts you can continue the installation from a network server (such as a Fedora mirror site). FWIW, you can also use PXE to boot any modern machine from a DHCP network server, and dispense with physical boot media altogether. The Installation Guide explains how to use these features:

http://fedora.redhat.com/docs/install-guide/fc6/