step 1: (installation)
(it might be possible that some packages are not needed but i installed these packages )

#sudo apt-get install libglib2.0-dev libgtk2.0-dev libglade2-dev libgnome-keyring-dev gedit gksu subversion build-essential autogen #automake autoconf intltool
#sudo apt-get install openvpn
#sudo apt-get install network-manager-openvpn
#sudo apt-get install gopenvpn (this may not be needed)

step 2: (Downloading Certificates and Key Files)

Download all the certificate files from pfsense->vpn->openvpn->
clientexport to /etc/openvpn
make all these file readable and executable for all by
#sudo chmod +rx * in /etc/openvpn

at this stage you can start the vpn but in text mode
the command is
#openvpn --config /etc/openvpn/pfsense-udp-1194-config.ovpn

Step 3 : (creating openvpn connection in graphical mode)

#/etc/init.d/network-manager start
click on network manager icon (it will appear on beside the sound icon on the taskbar on the top
right side)

vpn connections -> configure vpn -> import -> pfsense-udp-1194.ovpn
(browse this file.)
now this will create a vpn connection.
you have to modify this connection up to some extenct

step 4 : (modification/configuration):

go to vpn tab

gateway : it will take automatically don't make change

Type : password with Certificate (TLS) (default dont change)
username :
password :
User Certificate (browse this file)
CA Certificate (browse this file)
Private Key

click on advace button
go to TLS Authentication tab
check mark on use additional TLS authentication

Key File
Key Direction 1

Save The configuration

now again click on the network manager icon on right top
select vpn connections -> pfsense-udp-1194-config




(Basically the .ovpn file is important as its the main configuration file. In my case my openvpn server is on pfsense so I downloaded file from there. Your case may be different so only getting the .ovpn file will be the different procedure for you if you are not using pfsense.)