Excuse me, do you have Wi-Fi here?
What's the password?
I don't have an internet connection.
I don't have a network connection.
I'm logging on.
You have to register. (informal)
You have to log out. (informal)
Have you signed out? (informal)
You can google it. (informal)
I have to send an email.
I can't download the file.
I would like to install an app.
Can you share the link? (informal)