When it's your turn to bid, the bidding box appears and the screen shows "Your Turn"

Select your bid, and a pop-up will appear:

Pianola Play uses "self-alerts", which means you need to describe your own bids to your opponents if they are alertable or announceable. Your partner will not see your alert, but opponents will see a yellow exclamation point on your bid and they will see your explanation in the table chat.

Toggle the 'Alert' switch and describe your bid:

Click 'Confirm bid'.