Use your mouse to create a tag which spans the time until the first substitution or personnel change (your play-by-play should provide specific timing details). At the spot you'd like to begin, simply hold down your left mouse button and drag the tag to the spot on the timeline where the on-field roster changes. When you release your mouse button, an Attributes box containing your roster will show:
Click on the names of the players active in the match during the tag you just created. You can scroll down to the bottom of the box to see your full roster. When you click on a player's name, the box will darken. After selecting your players, be sure to press the 'Save' button.
Repeat those steps and continue creating 'Playing' tags throughout the rest of the game. At any time, you can right click on any tag to pull up the roster you have assigned to that clip. That roster will show in a pop-up box. Any alterations to that roster can be made, and will be saved when you press the 'Save' button.
Designating a 'Playing' tag for your game does a couple awesome things:
1) It allows you to pull up intersection filters whenever certain players are in the game. The instances where your search parameters 'cross' or 'meet' are considered intersections. For example, if you're searching for every scored goal a specific player was on the field for, you would filter for "Shot --> Result: Goal" and "Playing --> (x)", where '(x)' is the athlete you are searching for.
2) You can also pull up duration stats to see how many minutes a certain player logged in your match. This figure will be displayed when you search for stats by 'Athletes':