There are A LOT of tutorials and learning aids on the topic of evidence based practice. Here are some of the best.
Evidence based nursing is a part of the larger scope of evidence based practice. One of the most common definitions of evidence based practice comes from Dr. David Sackett. He describes EBP as:
"...the conscientious, explicit and judicious use of current best evidence in making decisions about the care of the individual patient. It means integrating individual clinical expertise with the best available external clinical evidence from systematic research."
Sackett, D. Evidence Based Medicine: What it is and what it isn't. BMJ 1996; 312:71-72.
The following diagram can help illustrate the components that go into evidence based practice: