Substitutions and tactical changes can be made throughout the match. The Substitutes and Tactics button will take you to the pre-kickoff screen and lets you make changes to the team tactics and formation. You cannot make a team talk at this stage however, only before the game, at half time and after the game.
Making a substitution is only necessary if a player is injured, or seriously underperforming. Players should have a rating of 6-10 throughout a match. Any lower than this and it's time for a pep talk with that player at half time or it may be time to swap him for another player in the same position.
If you’re in the middle of a promotion or relegation battle, the upper menu overlay will be vital to you during the match. This menu displays the current scores of matches taking place at the same time as your own, as well as displaying various in game statistical information.
The final in game screen is an overlay available via the left side of the screen. This displays real time statistical information such as possession, shots on target, corners, free kicks etc, while you can also make changes to your team’s style of play. For instance if it is late in the game and you have a comfortable lead, you might choose to play the “time-wasting” style.
It's worth trying out all of these options throughout the first few matches of the game. These are pre-season friendlies, suitable for experimentation of team selection, formation and tactical exploration.