Thank you, @yves_b. The solution is https://www.tp-link.com/us/support/faq/1591/. From the Wi-Fi, click advanced, then band, and you have the options for both, 2.4, and 5.

I live in a rural area and get my internet over an antenna. The 5GHz signal interferes with the antenna, so I must disable it. I don't need a separate SSID for 2.4 and 5. Maybe a switch with 2.4...