Welcome to the community forums!
I guess the best way to start is to ask and try to help into the forums.
Also you'll find a information on StackExchange and you can start diving into the http://devdocs.magento.com/
Another recomendation could be to be aware of Magento issues on Github: https://github.com/magento/magento2/issues (if you are technical, of course).
Reading this post will be helpful too: https://community.magento.com/t5/Welcome-to-the-Magento-Community/Start-here-and-hello-from-me/m-p/5...
Fianlly, you'll need to get your hands dirty with the platform.
@m_online Welcome to the best eCommerce community on the planet! There are always some great folks here or the other places that @Damian Culotta mentioned that are willing to help you become a Magento Rockstar!