how to build yocto kernel and boot loader with cyclone V with poky?

If you are looking for an SoC based board, the rocketboards.org site has linux distributions available for several development boards. Until you have more experience, I'd recommend staying with pre-built SD card images. There is documentation for building several distributions but it is a bit complex for a beginner to tackle. Its one of those everything must be right or it doesn't work things.