Update README.md

README.md

 # elphel393
 installation script for fetching and setting up building environment for elphel393 camera images
 
+### Get environment
 #### Stable
 ```sh
-$ ./setup.sh
+$ source setup.sh
 ```
 #### Latest
 ```sh
-$ ./setup.sh dev
+$ source setup.sh dev
 ```
+
+* Will switch directory to *poky/build*
+
+### Build targets all at once
+```sh
+$ bitbake u-boot device-tree linux-xlnx core-image-elphel393
+```
+* poky might require installing some packages, please check with the [Yocto Poky Manual][1] 
+* the results are in *poky/build/tmp/deploy/images/elphel393/*
+* for more info, read [here][2]
+* 
+[1]: http://www.yoctoproject.org/docs/2.0/mega-manual/mega-manual.html
+[2]: http://wiki.elphel.com/index.php?title=Poky_2.0_manual