Watch the above Panopto video from Academic Skills Centre (includes sub-titles) on literature searching using the CINAHL database. See below for summaries of this and other useful databases.
The following databases are worth noting. Not all will need to be used: for a standard search, 2-3 databases in total should be easily sufficient. However, if the project concerned is a detailed or systematic-style review, then up to 5-6 databases may be needed.