Install via pip:
pip install magicgui
conda install -c conda-forge magicgui
You will need to have a supported GUI backend also installed in your environment. Currently, the only supported backend is Qt, via qtpy (but open an issue if you would like to see a different backend supported).
pip install magicgui[pyqt5] # or pip install magicgui[pyside2]
or with conda:
conda install -c conda-forge magicgui pyqt5