Cannot capture non-local packets on MacOS

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Following the instructions on that Wiki allows me to capture radio packets, but I am interested in TCP/IP traffic.

For instance, if my iPhone and laptop are on the same network and I go to http://example.com/foobar on my iPhone, I want to see GET /foobar HTTP/1.1 etc. in Wireshark.

As per the info, to capture traffic between devices other than the capturing PC, you need to run monitor mode and then you'll also likely need to decrypt the WiFi traffic.

@grahamb I'm still not clear on how to capture that traffic. When I run monitor mode, all I see is 802.11 packets, and I don't know how to go about interpreting those.
For example, if my Wi-Fi network SSID is myWirelessNetwork, the password is password123 (the security is WPA2 Personal), and the MAC address of the router/BSSID is ab:cd:ef:12:34:56, how can I see the TCP packets being sent over the network?

Assuming you've captured the required info, you'll need to setup the decryption keys. There is a Wiki page on 802.11 Decryption.

Can you share your capture by uploading it to a public share, or at least display an image of the first 802.11 packet to check that you're capturing the correct thing?

I figured out how to set up the decryption keys. Now, I am having this problem.