The SixteenBall app runs on the iPhone, iPad, and under macOS.

This tutorial uses screenshots to call out key aspects of using the app to enter shots for a match.

Setup

When you first open SixteenBall, you will see the Match screen asking you to define the players.

The initial screen

Tap on the green PLAYERS link to enter their names and skill levels.

Enter two players and skill levels

Tap < Match to return to the Match page.

Return to the match screen

New Match will clear the players and allow you to enter new names (after a confirmation dialog).

Select Start Match to begin.

Start the match

Making shots

To record shots, select balls from the grid one at a time.

The first ball you select is the called shot. It will be marked with an * in the upper right-hand corner, which designates the ball that must be pocketed in the called pocket. If it isn't pocketed legally (i.e. because they player fouled), tap the ball again and it will be marked dead with a red line.

Next, select any additional balls that are pocketed on the same shot. They will be marked with a ball number in the upper right-hand circle. Once complete, select End shot from the menu at the bottom.

Select the 1-ball and 2-ball

End the first shot. The 1-ball and 2-ball are pocketed and pending their partner balls (two score two points apiece).
Select End shot again, indicating that no balls were pocketed. It is now Kate's turn and the 14-ball and 15-balls are now rogue.
Tap the 3-ball twice and it's marked dead.
End shot and it's automatically jrd's turn (because Kate fouled).
jrd legally pocket's the 4-ball and also sink's the 5-ball.
The 12-ball (in organic) is the required target (to complete the 4/12 pair). The 11-ball is also a valid pending partner ball -- as are the rogue 13, 14, and 15-balls.
The selection if the 11-ball is legally pocketed along with the 12-ball.
Selecting Clear shot resets all selected balls.
Alternately, selecting the 13-ball and 14-ball designates them at-risk because a pair is in process.
The 11-ball might also be included (quite a shot).
If the shot included the target ball (the 12-ball in this example), then there are no at-risk balls.