Download the source for the dependency
git clone https://github.com/ipa320/cob_perception_common.git
Dowload the source for this code
git clone https://github.com/ipa320/cob_people_perception.git
Add the paths to these files into your ~/.bashrc so that ROS knows that they exist. For example, if you cloned the file into your home directory, you would add the following lines to your ~/.bashrc. Make sure it's after the source declaration you made when you installed ROS:
export ROS_PACKAGE_PATH=$ROS_PACKAGE_PATH:$HOME/cob_perception_common
export ROS_PACKAGE_PATH=$ROS_PACKAGE_PATH:$HOME/cob_people_perception
At this point your going to have to update your ~/.bashrc either by closing your current terminal and opening a new one or using the command bash --login
Finally, go to the cob_people_detection directory by executing the command
roscd cob_people_detection
and build the package and all of its dependencies by typing
rosmake.
If you cannot execute roscd then you probably did the step of adding the files to your ~/.bashrc incorrectly. If you get an error while trying to run rosmake about not having sufficient permissions to make the build directory, then switch to the root profile by executing sudo -s and the try running rosmake again.
Please see the wiki.