Created documentation on how to fork a project.

doc/workflow/README.md

 # Workflow
 - [Feature branch workflow](workflow.md)
+- [Code forking workflow](forking_workflow.md)
 - [Project Features](project_features.md)
 - [Authorization for merge requests](authorization_for_merge_requests.md)
 - [Groups](groups.md)

doc/workflow/forking_workflow.md

+# Code forking workflow
+
+Forking a project to your own namespace is useful if you have no write access to the project you want to contribute
+to. If you do have write access, we recommend using the **[Code Branching Workflow](https://about.gitlab.com/2014/09/29/gitlab-flow/)**.
+
+## Creating a fork
+
+In order to create a fork of a project, all you need to do is click on the fork button located on the top right side
+of the screen, close to the project's URL and right next to the stars button.
+
+![Fork button](/forking/fork_button.png)
+
+Once you do that you will see a screen where you can choose the namespace, to where you want to add the fork. This page
+will contain the groups you have write access to. Choose one of the groups and the project will be added there.
+
+![Groups view](/forking/groups.png)
+
+After the forking is done, you can start working on the newly created repository. There you will have full Owner access,
+so you can set it up as you please.
+
+## Merging upstream
+
+Once you are ready to send your code back to the main project, you need to create a Merge request. Choose your forked
+project's main branch as the source and the original project's main branch as the destination and create the merge request.
+
+![Selecting branches](/forking/branch_select.png)
+
+You can then assign the Merge Request to someone so they can review your changes. After they have reviewed them, the will
+be added to the main project, if maintainer chooses to do so.
+
+![New merge request](/forking/merge_request.png)
+
+