when working on the HandsOn2 you will see that the notes for the tutorial are hosted at SLAC with rather "generic" instructions. I have translated them into 'iridium-able' commands ;-)

======================================================================================
BLOCK 1  getting the exercise code
======================================================================================

$ mkdir ~/HandsOn2          # make new working directory
$ cd ~/HandsOn2             # change to your new working directory
$ wget http://geant4.slac.stanford.edu/SLACG4TutorialHandsOn/HandsOn2/HandsOn2.tar.gz
$ wget http://geant4.slac.stanford.edu/SLACG4TutorialHandsOn/HandsOn2/HandsOn2-solution.tar.gz
$ tar xzf HandsOn2.tar.gz   # extract source code
# optionally extract in a similar way the solution. But please give the exercise a try first ;-)
$ cd HandsOn2               # change to newly extracted code
$ ls                        # have a look at the files
$ cd ..                     # let's go back to '~/HandsOn2' working directory

===================================================================================

and

===================================================================================
BLOCK 2  OPTION: SEPARATE build and source directory
===================================================================================

$ mkdir build-HandsOn2
$ cd build-HandsOn2
$ cmake ../HandsOn2
$ make
$ ./SLACtut

===================================================================================
RINSE AND REPEAT
===================================================================================
# ... modify files located under '~/HandsOn2/HandsOn2'
# compile the code at ~/HandsOn2/build-HandsOn2
$ make
# when you issued 'cmake ../HandsOn2' those two folders got linked. It would just work
===================================================================================

OR

===================================================================================
BLOCK 2  OPTION: SAME build and source directory
===================================================================================

$ cd HandsOn2
$ cmake .
$ make -f Makefile
$ ./SLACtut

===================================================================================
RINSE AND REPEAT
===================================================================================
# ... modify files located under '~/HandsOn2/HandsOn2'
# compile the code directly at ~/HandsOn2/HandsOn2
$ make -f Makefile
===================================================================================

Happy coding ;-)