You should have started your project from the Silverstripe installer module and the CMS CCL Recipe module for the maximum level of compatibility with the platform.
For custom development work for your website, the best source of technical information for SilverStripe CMS development is the Official Silverstripe CMS developer documentation.
With Composer you can easily add to the modules that are included in the project. Full instructions can also be found in the Silverstripe CMS documentation.
Avoid changing modules directly. Instead, SilverStripe CMS's architecture allows safe customisation through:
To gain a deeper understanding of how the Silverstripe CMS and framework can be used to develop custom solutions, we recommend going through the Silverstripe CMS online lessons and searching through the Official Silverstripe CMS development documentation.