Anyway, the means of adding the variable differs but generally the consensus is you should add the directive to your .bashrc file as it applies to both the cli and the gui environment.
You will find your .bashrc file in your home directory. To edit it type
gedit ~/.bashrcThis will open the file in gedit ready for you to edit
Scroll to the bottom of the file and add
PATH=$PATH:/some/path/you/would/like/to/add;export PATHSave this file. You may need to reopen your terminals or relogin for it to take affect. This will add the "/some/path/you/would/like/to/add" path to your PATH environment variable. Now any binary you have residing in this path will be available directly.