I would assume that you want to install IntelliJ Idea because you want to program in Java. And because of that, I would also assume that you already have JDK installed as I won't be elaborating on that, sorry. ^^
- Please download IntelliJ Idea from here.

- You will see instructions from the Jetbrains website itself :
Unpack the idea-9.0.4.tar.gz file using the following command:
tar xfz idea-9.0.4.tar.gz
- You should now have the folder containing all the files you extracted. Let's rename the folder to idea9 to make things simple. You can rename it to whatever you want.
- Let's copy that directory to /usr/lib by executing the following command :
sudo cp -R idea9 /usr/lib - Now, you will need to configure JDK_HOME, because idea.sh will be looking for it and won't run unless you have that variable set.
sudo gedit /etc/environment
- Add this line :
export JDK_HOME="/usr/lib/jvm/java-6-sun/"
- ... and add the following value to your PATH variable.
/usr/lib/idea9/bin
Make sure all the values in your PATH variable are separated by colon (:).
- Logout, then login again.
- Now you can run idea.sh from your terminal. ^^
To make things even easier, I added a
Custom Application Launcher to my panel.
- Right click on your panel, then click Add to Panel...
- Select Custom Application Launcher and click the Add button.
- Enter the following values :
Name : IntelliJ Idea 9.0
Command : idea.sh
- You can even put the logo of IntelliJ Idea which can be found in the directory /usr/lib/idea9/bin.
- Click OK. Now you'll have a shortcut on your panel. You will just need to click on it to open IntelliJ Idea. ^^