As far as I know the gui is built in and should work when asterisk is loaded. I download the .tar files for Freepbx, Asterisk, Zaptel, Libpri, Asterisk sounds, and add-ons. The files are unzipped installed and configured by using a script. Here is what I am using.
#UPDATED 2-21-06
#
#How to Install Asterisk and FreePBX on CentOS 4
#==========================================
#KISS(Keep It Simple Stupid)
#CentOS 4 installation:
#You will need the Centos 4 "Server Edition"
#I used graphical install mode
#Disable the SELINUX and Firewall
#Install the "minimal" package (it's at the bottom of the package selection)
#
#This guide is now executable!!!!
#
#run "yum update" and then reboot prior to executing this script!
#execute this script by entering "sh guide.txt" at the linux prompt
#-----------------------------------------------------------------------------------
clear
yum -y install gcc libxml2-devel libtiff-devel mysql-server php-gd php-mbstring php-mysql kernel-devel bison ncurses-devel audiofile-devel libogg-devel openssl-devel httpd
rpm -ivh
#------------------------------------------------------------------------------------
cd /usr/src
wget
tar -zxvf freepbx-2.2.0.tar.gz
mv freepbx-2.2.0 freepbx
#--------------------------------------------------------------------------------------
wget
tar -zxvf asterisk-1.4.9.tar.gz
mv asterisk-1.4.9 asterisk
wget
tar -zxvf zaptel-1.4.4.tar.gz
mv zaptel-1.4.4 zaptel
wget
tar -zxvf libpri-1.4.1.tar.gz
mv libpri-1.4.1 libpri
wget
tar -zxvf asterisk-addons-1.4.2.tar.gz
mv asterisk-addons-1.4.2 asterisk-addons
wget
tar -zxvf asterisk-sounds-1.2.1.tar.gz
mv asterisk-sounds-1.2.1 asterisk-sounds
#-------------------------------------------------------------------------------------------
cd /usr/src/zaptel
#mv ztdummy.c ztdummy.c.orig
#sed "s/if 0/if 1/" < ztdummy.c.orig > ztdummy.c
#cd /usr/src/kernels/`2.6.9-55.0.2EL-i686 -r`-`2.6.9-55.0.2EL-i686 -m`/include/linux/
#mv spinlock.h spinlock.h.orig
#sed "s/rw_lock_t/rwlock_t/" < spinlock.h.orig > spinlock.h
cd /usr/src/zaptel
#make linux26
make clean; make install
make config
cd /etc/sysconfig
mv -vf zaptel zaptel.old
touch zaptel
echo "TELEPHONY=yes" >> /etc/sysconfig/zaptel
echo "#DEBUG=yes" >> /etc/sysconfig/zaptel
echo 'MODULES="$MODULES ztdummy"' >> /etc/sysconfig/zaptel
modprobe zaptel
modprobe ztdummy
echo "modprobe ztdummy" >> /etc/rc.d/rc.local
#-----------------------------------------------------------------------------------------------
cd /usr/src/libpri
make install
#-----------------------------------------------------------------------------------------------
cd /usr/src/asterisk
mkdir /var/run/asterisk
make install
make config
#-------------------------------------------------------------------------------------------------
useradd -c "Asterisk PBX" -d /var/lib/asterisk asterisk
chown asterisk /var/lib/php/session/
sed -i "s/User apache/User asterisk/" /etc/httpd/conf/httpd.conf
sed -i "s/Group apache/Group asterisk/" /etc/httpd/conf/httpd.conf
#---------------------------------------------------------------------------------------------------
/etc/init.d/mysqld start
cd /usr/src/freepbx
mysqladmin create asterisk
mysqladmin create asteriskcdrdb
mysql asterisk < SQL/newinstall.sql
mysql asteriskcdrdb < SQL/cdr_mysql_table.sql
mysql -vv -e "GRANT ALL PRIVILEGES ON asteriskcdrdb.* TO asteriskuser@localhost IDENTIFIED BY 'amp109'"
mysql -vv -e "GRANT ALL PRIVILEGES ON asterisk.* TO asteriskuser@localhost IDENTIFIED BY 'amp109'"
mysql -vv -e "flush privileges"
mysqladmin -u root password '@madusa01'
#--------------------------------------------------------------------------------------------------------
cd /usr/src/asterisk-addons
cp Makefile Makefile.orig
sed -i 's/SOURCE/SOURCE -DMYSQL_LOGUNIQUEID/' Makefile
make && make install
#---------------------------------------------------------------------------------------------------------
cd /usr/src/asterisk-sounds
make install
#----------------------------------------------------------------------------------------------------------
clear
ifconfig eth0
cd /usr/src/freepbx
./install_amp
mkdir /var/lib/asterisk/sounds/custom
chmod 775 /var/lib/asterisk/sounds/custom
echo /usr/sbin/amportal start >> /etc/rc.local
chkconfig --level 345 httpd on
chkconfig --level 345 mysqld on
chkconfig --level 345 ntpd on
#------------------------------------------------------------------------------------------------------------
cd /usr/src
wget
rpm -i wanpipe-modules-2.6.9-34.0.2.ELsmp-2.3.4-3.i686.rpm
wget
rpm -i wanpipe-util-2.3.4-2.i686.rpm
#------------------------------------------------------------------------------------------------------------
echo "Congratulation!!!...you can reboot the system now."