Once you've built an OS image, you'll need to transfer it to your board.
The IDE lets you communicate with your target and download your OS image using either a serial connection, or a network connection using the Trivial File Transfer Protocol (TFTP). If your board doesn't have a ROM monitor, you probably can't use the download services in the IDE; you'll have to get the image onto the board some other way (e.g. JTAG).