Update README.md (#19)

README.md

@@ -74,9 +74,19 @@ We have many channels for community members to discuss, ask for help and feedbac
 | Community events | Including meetups, webinars, conferences, and more events, visit the [Events page](https://yandex.cloud/ru/events?page=0&services=246) and subscribe events calendar.  |
 | Documentation | [Official documentation](https://yandex.cloud/en/docs/managed-greenplum/) for Managed Database. You can explore it to discover more details about us. |
 
-
 ## Contribution
 
+Open-gpdb is a free and open project and we appreciate to receive contributions from our community.
+
+### Contributing code changes
+
+If you would like to contribute a new feature or a bug fix, please discuss your idea first on the GitHub issue. If there is no issue for your idea, please open one. It may be that somebody is already working on it, or that there are some complex obstacles that you should know about before starting the implementation. Usually there are several ways to fix a problem and it is important to find the right approach before spending time on a PR that cannot be merged.
+
+### Provide a contribution
+To make a contribution you should submit a pull request. There will probably be discussion about the pull request and, if any changes are needed, we would love to work with you to get your pull request merged.
+
+Follow this link to have more information about build and test system: [Build readme](README.build.md)
+
 ## Acknowledgment
 Thanks to PostgreSQL, Greenplum Database and other great open source projects to make our project has a sound foundation.