If the Sage app is at /Applications/SageMath-8.0.app, starting the Jupyter notebook
with the option you want can be achieved by typing the following in a terminal.
$ /Applications/SageMath-8.0.app/Contents/Resources/sage/sage -n jupyter --ip '*'
(type everything that follows the $ prompt, but not the $ prompt itself).
To make this simpler, you could place a symbolic link to the Sage executable
somewhere in your path. For this, type the following in a terminal
$ sudo ln -s /Applications/SageMath-8.0.app/Contents/Resources/sage/sage /usr/local/bin
and enter your password when asked to.
Explanation: ln -s TARGET LOCATION places a symbolic link to TARGET in LOCATION.
Here the target is the Sage executable, /Applications/SageMath-8.0.app/Contents/Resources/sage/sage,
and the location is /usr/local/bin. The command is called with sudo ("super-user do")
because you need admin rights to write in /usr/local/bin.
From then on, you can call Sage in a terminal by just typing
$ sage
and you can launch the Jupyter notebook by typing
$ sage -n jupyter
and you can launch the Jupyter notebook accessible from all IP addresses by typing
$ sage -n jupyter --ip '*'
If in addition you type the following in a terminal,
$ sudo sage -c "install_scripts('/usr/local/bin')"
then shortcuts to start GAP, PARI/GP, R, Singular, etc. will be placed in /usr/local/bin
so that you can launch those by typing in a terminal:
$ gap
$ gp
$ R
$ singular
etc.
