To make a Zoom virtual background for yourself, I believe this is easiest on the Zoom app on a laptop (not on a phone*).
If you've only joined Zoom meetings by anonymously clicking a link, you also have to have a free registration in Zoom (email required). OK. At that point, you can quickly click Settings and Virtual Background, and either pick a pre-fab background or upload a favorite photo.
I put this off for a month, and it took 15 seconds to do it. (My landscape is currently Runyon Canyon in the Hollywood Hills near my house).
Quick screen shot of the steps in Windows, below. If my pic below isn't clear enough, you can also find many sources of free instructions on Google or YouTube.
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*One source says Virtual Backgrounds may work on iPhone 8 or later and iPad Pro or 5th gen iPad. It definitely works, quick and easy, on the laptop apps.