Add contributing to readme

README.md

@@ -4,7 +4,7 @@ This is a repo to diagnose issues in glider data such as CTD thermal lag.
 
 This is a work in progress, all contributions welcome!
 
-### Instal
+### Install
 
 Install from PyPI with
 
@@ -28,3 +28,12 @@ Check out the example notebook `notebooks/demo.ipynb` for example functionality
 
 As input, glidertest takes [OceanGliders format files](https://github.com/OceanGlidersCommunity/OG-format-user-manual)
 
+### Contributing
+
+All contributions are welcome! Please clone the repo and install a local development version of `glidertest` as described in the Install section above. All new functions should include tests, you can run the tests locally and generate a coverage report with:
+
+```sh
+pytest --cov=glidertest --cov-report term-missing  tests/
+```
+
+Try to ensure that all the lines of your contribution are covered in the tests.