The simplest way to install ipyannotations is via pip:

pip install ipyannotations

If you installed via pip, and notebook version < 5.3, you will also have to install / configure the front-end extension as well. If you are using classic notebook (as opposed to Jupyterlab), run:

jupyter nbextension install [--sys-prefix / --user / --system] --py ipyannotations

jupyter nbextension enable [--sys-prefix / --user / --system] --py ipyannotations

with the appropriate flag. If you are using a Jupyterlab version below 3.0, install the lab extension with:

jupyter labextension install ipyannotations
jupyter lab build