A collection of useful links to relevant documentation.
https://jupyter.org/documentation contains a lot of useful links to relevant documentation.
Documentation for jupyter lab:
https://jupyterlab.readthedocs.io/en/latest/
Documentation for the jupyter notebook interface:
https://jupyter-notebook.readthedocs.io/en/stable/
General nbgrader documentation:
https://nbgrader.readthedocs.io/en/latest/
For an example of a workflow using nbgrader extensions:
https://github.com/havardei/notebooks/blob/master/doc/tutorial.md