Hi,
You can find all available documentation
here.
If you are using portal engine templates, I recommend read through the "Kentico CMS tutorial (portal engine)". If you are using ASPX templates - "Kentico CMS Tutorial (ASPX templates)".
Also, please use the "Kentico CMS Developer's guide" where you can find very useful information at one place.
Best regards,
Juraj Ondrus