The process of creating the tracking data needs something called tracking markers. You will need several of them to create useful tracking content. In this particular case, where we have a screen, you will need at least four markers.

Look to the left sidebar in your Movie Clip Editor, and you will find all the necessary options for managing tracking data (Figure 8.4):

Before you add any markers, make sure you have frame 1 as your current frame.

To add a marker, you can use the Marker section in the sidebar and choose Add. Once you hit the Add button, click anywhere in the video to create the small squared marker (Figure 8.5):

You can click and drag the marker to a corner of the smartphone screen. Blender will even magnify the marker on the left to help you locate the marker in the best possible location (Figure 8.6):

You can use the same shortcuts to select and manipulate the markers that you use most often in Blender. Right-click to choose a marker and use the G key to move it.

On the right side of your marker, you will see a small line with a square in one of the sides. If you click and drag on that square, you will be able to scale up and down the marker size.

After adding the first marker, use the Add button to create another marker and make sure it is at another corner of the screen. Repeat the process two more times until you have four markers (Figure 8.7):

We have the markers but no tracking whatsoever. If you play the video, there won't be any movement in the markers. To make Blender start tracking the video, you will use the Track options on the left sidebar.

There you will find a track section and controls. The play button will trigger continuous tracking from the current frame until the end. If you go to the next button, you will get single frame tracking. By using the buttons on the left, you will get the same behavior in the opposite direction (Figure 8.8):

Make sure the project is using the full length of your video before you start tracking. In our case, the video will end on frame 289.

Blender will only track the selected markers, and if you wish to follow all four of them, you must choose them all. Use the A key to quickly select all markers and hit the play button in the Track options. You will see the tracking graph showing that Blender is following motion in your video.

With the tracking data ready, you can hit the play button from the Timeline, and you will see all four markers following the screen.