Thanks for checking out the bingo game! We are using it by having meeting attendees open it via the link sent out in an email prior to the meeting or even a link in the chat window of a meeting. They have it open in a separate window from the meeting window, and on a separate monitor, if they have two monitors. That way, they don't miss any of the meeting content.
To assign cards, the meeting host can quickly run down the participant list in the beginning of the meeting and assign numerically: Tom, you take card 1, Daisy - card 2, Bob - card 3, etc... Our teams are small, so this works well. For larger meetings, you may just need to ask participants to pick a random card, knowing some will have the same cards as others.