If you want to get maintained version of Arduino IDE then you install if from the repository:
sudo apt-get update
sudo apt-get install arduino
However, this way you get a very old version (currently 1.0.5) which is not updated too often.
If you already installed via apt-get you can uninstall the packages:
sudo apt-get remove arduino
sudo apt-get autoremove
Better way is to download and install Arduino IDE yourself.
Open a terminal window (e.g. by pressing CTRL-ALT-T), and run uname -m to check if you are running 32 bit or 64 bit platform:
uname -m
See output:
x86_64 ==> 64-bit kernel
i686 ==> 32-bit kernel
Go to Arduino Download page on https://www.arduino.cc/en/Main/Software and download the 32 bit or 64 bit version, depending on the Ubuntu version installed on your computer.
In a terminal window extract the package and move it to your preferred location, e.g. /opt. You need sudo rights to move it to /opt. Finally, run the install script if you want to start the IDE graphically (adds desktop icon, MIME type, default application for .ino). See the example commands below for installing the latest 32 bit version as of the time of writing.
cd ~/Downloads
tar xf arduino-1.6.7-linux32.tar.xz
sudo mv arduino-1.6.7 /opt
/opt/arduino-1.6.7/install.sh
You can also start the IDE from terminal:
/opt/arduino-1.6.7/arduino