A good place to get started is to familiarize yourself with the concepts used in Gru.
Afterwards you should check the installation document which provides information on how to obtain and install Gru.
Once ready with that check the quickstart guide, which will walk you through your first steps with Gru.
For setting environment variables, make sure to check the environment variables document.
In order to automatically start your minions during boot-time, you should check the document for enabling services during boot-time.
You should also check the documentation of available resources that you could use in your code.