Using virtual media from iDrac, you can map CD/DVD, map removable disk or attach media. And then you just need to choose to boot from the virtual media.
Many modern servers don't come with an optical media drive, including NAS servers such as the Dell R410. Installing from a USB stick may work, but some Windows installations fail with "No CD/DVD driver present" warnings. At this point, you can either slipstream a custom install with the drivers, or just boot and install with your iDRAC card.Example:
CIFS — //<IP to connect for CIFS file system>/<file path>/<image name>
NFS — <IP to connect for NFS file system>:/<file path>/<image name>