Install Composer is easy. You simply download the latest binary file(*.phar) from https://getcomposer.org/download/. Set it executable and then run it.
# Download the latest version. wget https://getcomposer.org/composer-stable.phar # Make it executable. chmod +x composer-stable.phar # Move it to path where you can run it anywhere. mv composer-stable.phar /usr/local/bin/composer # Test it out. It should show the version number. composer --version
Here are some examples on how to install Drupal modules using Composer.
# Install Markdown module. cd DRUPAL_ROOT_DIR composer require 'drupal/markdown:^2.0' # Install GeSHi Filter for syntax highlighting module. cd DRUPAL_ROOT_DIR composer require 'drupal/geshifilter:^1.3'