This message was posted on behalf of Intel Corporation
Thanks for reaching out!
The BSP guide you mentioned is a little bit out of date, nevertheless, you can find the instructions on how to build Edison's image in a file included on the source code. You can find the latest source code in https://iotdk.intel.com/src/3.5/edison/. The file with the instructions is called README.edison.
In case you have any doubts about how to use the BSP and its tools, I'd suggest you to read Yocto's Mega Manual (http://www.yoctoproject.org/docs/1.7.3/mega-manual/mega-manual.html), this documents contains a lot of useful information about Yocto's BSP and all of its tools.
I hope this helps.