You might get a message like:
bind: Address already in use
channelsetupfwd_listener: cannot listen to port: 8888
Could not request local forwarding"
This means that another process is using that port and you need to start the everything again with a different port number. Otherwise, if all has gone well, the terminal will appear to be hanging (the  "-N" flag prevents any more user input) and the SSH tunnel should be open. To use the Notebook, open a browser on your computer and paste in the link provided in the first terminal (e.g. http://localhost:8888). Congratulations, you should now be looking at the familiar Jupyter Notebook file browser.