Boris 24
Open System Preferences and select Sharing. If you don't see the below screen, click on the icon showing 12 dots.
Click on Sharing.
Now click on the box beside Internet Sharing.
Beside 'Share your connection from:' choose Ethernet.
Below that, beside 'To computers using:' choose Wi-Fi.
Next click Wi-Fi Options, this will give you the option to choose a password so that strangers can't jump on your Wi-Fi (it should be least eight characters). Next to Security choose WPA2 Personal and then enter your Password and verify it. (WPA2 is the 802.11i standard for encryption.)
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Anonymous
What exactly do you hope to accomplish by doing that? Just connect the iPhone to the same network the MacBook is already on.
Bort
Search engines are your friend.
https://www.macworld.co.uk/how-to/share-mac-wifi-hotspot-3490420/