If you want a ready made image for your embedded device you can use their online builder available here.
I recently faced a situation where I had to enable SPI driver in Angstrom distribution for beagleboard. For that I had to custom compile the Linux kernel with the McSPI module enabled since it was not enabled in the default builds.
Create a folder in your home directory called "openembedded"
$mkdir ~/openembedded $cd ~/openembedded
Download the setup scripts for Angstrom using git
$git clone git://git.angstrom-distribution.org/setup-scripts $cd setup-scripts
Start the build process for beagleboard. This will download the "bitbake" which is only a tool used to build packages and "openembedded" system which provides the "recipes" of the packages for the "bitbake" tool.
./oebb.sh config beagleboardNote: Replace beagleboard with your embedded machine name. Also note that "openembedded" git download is more than 700 MB.
Load the script file created in the previous step. You need to do this everytime you want to build packages from a new terminal, or you can add this line to the ~/.bashrc file
Build your first package the famous "nano" command line editor
Now, the real thing is to build the kernel image from source