How to install the new version of asterisk is quite simple. If you are already familiar with updating it, you have nothing to worry about. The installation should go smoothly. If you are not familiar with it here are some of the steps.
yum groupinstall "Development Tools"
git clone https://github.com/asterisk/pjproject.git
./configure --prefix=/usr --enable-shared --disable-sound --disable-resample --disable-video --disable-amr
Install Asterisk 12
svn co http://svn.asterisk.org/svn/asterisk/branches/12/
yum install sqlite-devel
make menuselect(optional) "cmenuselect"(worked for Asterisk 12)
make & make install
Go back to the asterisk directory, it should be
Be sure to run the install..prereq in
make menuselect(for asterisk modification)