Update installation instructions

Author: martinRenou

README.md

@@ -40,8 +40,9 @@ jupyter labextension install @jupyter-widgets/jupyterlab-manager
 jupyter labextension install .
 ```
 
-If you are using Jupyter Notebook 5.2 or earlier, you may also need to enable
-the nbextension:
+And you use the classical Jupyter:
+
 ```bash
-jupyter nbextension enable --py [--sys-prefix|--user|--system] ipycanvas
+jupyter nbextension install --py --symlink --sys-prefix ipycanvas
+jupyter nbextension enable --py --sys-prefix ipycanvas
 ```