The preferred way to install this extension is through composer.
Either run
php composer.phar require --prefer-dist open-ecommerce/yii2-kartik-trivalent "dev-master"
or if you have composer installed globaly
composer require --prefer-dist open-ecommerce/yii2-kartik-trivalent "dev-master"
or add
"open-ecommerce/yii2-kartik-trivalent": "dev-master"
to the require section of your composer.json file.
Depending on your minimun composer requirements defined in your composer.json you will need to add the repository:
"repositories": [
{
"type": "vcs",
"url": "https://github.com/open-ecommerce/yii2-kartik-trivalent"
},
...
If you have any questions, feel free to ask.