No one tutorial is sufficient to instruct students how to use a comprehesive database such as CINAHL.
Most useful are those resources that answer specific user queries
This video explains how to use Boolean Operators ( AND, OR and NOT) in a CINAHL literature search
Shows how to use keywords to make a useful literature search
Listen only to the first 8 minutes- the remainder is specific to Pace University's version of CINAHL
This Library has CINAHL Plus, a version of CINAHL with more features
No one tutorial can show you how to use such a comprehensive database as PubMed
The link below offers many videos, each explaining one or more aspects of PubMed use