Add citation hint to README

README.md

@@ -18,10 +18,12 @@ Process uses a mixture of tracking and testing to ensure code reliability. Tests
 ## Development
 Please see the CONTRIBUTING.md for guidance on how to contribute to PROCESS. Further information is found in the development section of the [documentation](https://ukaea.github.io/PROCESS/).
 
-
 ## Publications
 A list of publications using PROCESS is given [here](https://ukaea.github.io/PROCESS/publications), including two papers outlining the physics and engineering models in PROCESS.
 
+## Citing PROCESS
+If you use PROCESS in your work, please cite it using the "Cite this repository" link in the "About" section of the repository.
+
 ## Contacts
 [James Morris](james.morris2@ukaea.uk)