Complete readme

README.md

@@ -15,3 +15,15 @@ $ ./build.sh
 ```
 
 The product page and the documentation should be built and extracted under the target directory.
+
+To release a new version:
+
+* Run the following git command to add another git submodule:
+
+```
+ git submodule add -b $branch -f --name "versions/$branch" [email protected]:BlueBrain/nexus.git versions/$branch/
+```
+
+* Update the versions/versions.md file and create the new current / push the previous in the older releases
+* Update the current branch in the build.sh file
+* Example: https://github.com/BlueBrain/nexus/pull/5142