Go to Career Mode and start a new career as a Manager, the settings don't matter but you will want to put the match difficulty on Amateur and Half Length as long as possible to make this achievement easier for you. When the season starts, skip to your first match (it can be a friendly) in the calender then play the match. Before the game, go to Team Management and select a 4-3-3 formation, this is not essential but it will make things easier for you. Now start the match and as soon as it begins pause the game and go to Team Management again. Now substitute the 3 strikers/forwards you have on the pitch for any 3 players that are on the substitutes bench. When there is a break in play (e.g. the ball goes off, a foul is commited) the substitutes will be made. Now just score a goal with any of the players you just brought on from the substitutes bench and the achievement is yours.