join in
US /dʒɔɪn ɪn/
UK /dʒɔɪn ɪn/

1.
unirsi, partecipare
participate or become involved in an activity with others
:
•
Everyone was singing, so I decided to join in.
Tutti cantavano, così ho deciso di unirmi.
•
Don't be shy, just join in the game!
Non essere timido, unisciti al gioco!