Firstly, please do run these following commands inside the Terminal or CMD:
conda update anaconda-navigator conda update navigator-updater
Following which, the problem for the instruction provided below will be resolved. For a windows system, if one has the anaconda software installed, you can simply try this:-
pip install opencv-python or conda install -c https://conda.binstar.org/menpo opencv
If you are using the linux software, then you can try:
pip install opencv-python or conda install opencv
Finally, if you are using the anaconda software, then you may simply use this as well excluding the need to add the menpo channel:-
conda install -c conda-forge opencv