Update README.md

README.md

 # OpenACC
 
-Training Material/GPU Programming/OpenACC
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+Training Material/GPU Programming/OpenACC
+
+The present project contains code and exercises using OpenACC for programming GPUs.
+
+## How to contribute
+
+Any contributions (new exercises and examples, bug fixes, improvements etc.) are
+warmly welcome. In order to contribute, please follow the standard
+GitLab workflow:
+
+1. Fork the project into your personal space
+2. Create a feature branch
+3. Work on your contributions
+4. Push the commit(s) to your fork
+5. Submit a merge request to the master branch
+
+As a quality assurance, the merge request is reviewed by PRACE staff before it is accepted into main branch.
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