Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -16,3 +16,21 @@ Some things to consider:
 * Write tests
 * Follow the existing coding style
 * Write a [good commit message](http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html)
+
+## Setup your fork
+
+Fork this repository! Once you have a copy of this repo on your own account, clone this repo to your computer by typing in something like:
+
+1. `git clone https://github.com/sirixdb/sirix.git`
+
+  (Replace the URL with your own repository URL path.)
+
+2. Run `cd sirix`. Then, set up this repository as an upstream branch using:
+  * `git remote add upstream https://github.com/sirixdb/sirix.git`
+
+  Now, whenever you want to sync with the owner repository. Do the following:
+  * `git fetch upstream`
+  * `git checkout staging`
+  * `git merge upstream/staging`
+
+  Note: You can type `git remote -v` to check which repositories your `origin` and `upstream` are pointing to.