To put this folder on the PATH environment variable type
This appends the folder to your existing PATH, however, it is only active for your current terminal session.
If you want it to be automatically set, it depends on the shell you are using. For bash, you can append this line to $HOME/.bashrc using your favorite editor or type the following on the shell
echo 'export PATH="$PATH:$HOME/.composer/vendor/bin"' >> ~/.bashrc
In order to check if it worked, logout and login again or execute
on the shell.
Hope this works!!