Either download and unpack the archive into application/libraries/Loggly or use git submodules. Use sudo if you're in a restricted directory.
Run this in Terminal from your CodeIgniter root directory:
git submodule add git://github.com/frankpinto/codeigniter-loggly.git application/libraries/Loggly
git submodule init
git submodule update
Either put it in the application/libraries folder manually or run this in Terminal from your CodeIgniter root directory:
wget https://github.com/frankpinto/codeigniter-loggly/archive/master.zip
unzip master.zip
mv codeigniter-loggly-master/ Loggly
Add your loggly key to your default config file (key below is non-working) and any custom environment config files you've created
application/config/config.php
application/config/(development|staging|whatever)/config.php
/* Loggly config data */
$config['loggly_key'] = '83hfni39-x3j9-2918-bc4j-393ivmklwi39';
From any controller action:
$this->load->library('loggly');
$this->loggly->send('Hi Loggly!');
PHP bindings taken from cowlby's PHP Loggly Bindings library