Update How To Release a version docs

CONTRIBUTING.md

@@ -31,6 +31,17 @@ Metacello new
 
 Remember the docs are licensed under a CC Attribution-ShareAlike license. 
 
+## How to release a new version
+
+The master branch should always contain a releasable version, so all the test cases must be passing. The released versions are managed as tags using the GitHub releases support.
+1. The following code changes should be made before the release:
+ - Update version number in `package.json`
+ - Update version number in `WillowNamespaceFileMetadataLibrary class>>version`
+ - Fix the test cases related to version numbers
+2. Merge this changes to master
+3. Edit the release draft, add any missing info about the release and publish it
+4. Make the public announcement
+
 ### Useful References:
 
 - [Bootstrap Documentation](https://getbootstrap.com/docs/3.3/)