Upgrade Mito by opening the terminal and virtual environment that you installed Mito on. Make sure you have the most up to date version of the mitoinstaller, by running the command:
pip install mitoinstaller --upgrade
Then, actually run the upgrade process:
python -m mitoinstaller upgrade
After running the above commands, restart your JupyterLab kernel, and refresh your browser page to load the new version of Mito.
To see what is new in the Mitosheet since you last looked, check out the release notes.