Chroma keying

How i can perform 4 camera chroma keying white 4 deferent backgrounds? Using ATEM 4 M/E Brodcast Studio.

There are a few different ways you could do this, but I think the most optimal way would be to set up a macro function. The keying itself should be done on an upstream keyer. You would set up a macro for each of your cameras that would configure the upstream keyer with that camera source and background source. Set up the macro so it loads the upstream key to preview, then you can take it/transition to it just like any other source.

THX very much , Adam! Do You have any demo video , how its sholde be done?
I m only one week in thise buissnes so every thing ist difficulty