Choose a single toy and sit facing each other, close enough to hand it across.
Hold it, play with it briefly and say 'my turn.' Then pass it over and say 'your turn.' Keep each turn short — five seconds is plenty at first.
Name the turn every single time. The words are what make the pattern visible; without them it is just an adult taking a toy away.
Turn-taking is the structure underneath conversation, friendship and classroom life, and it has to be learned before it can be expected. Naming each turn gives the child a predictable rhythm to lean on rather than a rule to resent.