For the new cruisers, here is a tip....save your activities before the booking time, it makes booking easier. Some of the activities and excursions are similar. You have the option of looking first at your saved activities and you will get a menu for that.
You have to select from the screen, dining or ports of call....(I'll need to check this again for you).
The screen will ask you to book a member of the party for the event. ie you....and it will have a drop down menu of the people you want to include in that activities. So, if it is you, DH, DD and DS, for Polo's you select you and DH.
Then you can book a time, there will be a drop down menu with the dates and times remaining.
You can continue to book or you can confirm with what you have. I suggest confirming after each even to avoid the problem with someone taking your spot. This may not be a problem as much on this cruise but on some, by the time you work through all the bookings, the first time is gone. For this cruise, since we only have one sea day, that may well be the one that is most taken.
When you are completed, you will have an option to print all the activities you selected. You can also print after each selection or note the reservation number.
After you have booked you can go back and modify if needed, like - hypothetically if you forgot to add your DH to the reservation...ooopisie. Just an example of course, I would never do that

Nope, just an example....
Hope this helps.