I found this from somewhere else it’s really simple. So I say two words and the next person removes one of the words and replaces it with another word, it doesn't matter which word you remove and you could add the new word either before or after the remaining word as long as the two words make sense when used together.

For example, I could say “back door” and the next person could remove “back” and add the word “front” to make it “front door”

Or I could remove the word "door" and replace it with the word "pack" to create "back pack”

I'll start with the words "Thunder Storm"