You should include the autoloader the composer has generated. PHP: <?phprequire_once "vendor/autoload.php"; Then you are good to import your composer libs. PHP: <?phprequire_once "vendor/autoload.php";use my\composer\Library;
If you want to use composer in your plugin, you should place the composer.json next to your plugin.yml, then composer init before compiling your plugin, then in onLoad() of your plugin, add this line: PHP: require $this->getFile() . "ventor/autoload.php"; If you use it with Poggit, you must pre-install it locally, then also push the vendor files to GitHub and tell Poggit to include vendor/ in the compiled phar, because Poggit does not install composer for plugins.
Still don't understand why people would want to waste their time waiting for a reply on a forum. A quick Google search could've literally given you hundreds upon thousands of results about composer tutorials. You should probably read the composer documentation before you start using it.
The question is, if you don't know what composer is, why do you even say that you want to use composer?