You're playing a 4-4-1-1 system.
Think of your team as a series of partnerships: the two centre backs, the two central midfielders, the two left sided players, the two right sided players and the front two. You want players in roles and with attributes that will complement each other. You also need to break the lines - have players advance beyond their starting positions and others drop to create space, etc - rather than playing in two straight rows of 4 with the top two remaining one behind the other.
For example, in my 4-4-1-1 the left back is on attack mode with the left winger on support. So the full back constantly overlaps down the flank and delivers crosses from the byline. The winger crosses from deep, typically from the angle of the penalty area, towards the back post. The right winger is on attack mode, so he's more likely to be in position to connect with those crosses. His role also requires him to attack the byline and get crosses in. The right back behind him is on support mode. He's only going to overlap when providing a second wave attack when the initial attempt to get forward has run into defensive traffic. The full back crosses from deep to the Target Man.
Centre backs. I prefer a Bruce-Pallister style of partnership where one of them is a proper combative Stopper, in the Martin Skrtel mode, whereas the other is a Ball Playing Defender like John Stones. I require them both to be good in the air and strong in the tackle, but partnering two different types together makes them more effective as a pair.
Central midfielders. Essentially, one should be more defensive and the other more attacking. How defensive and how attacking is up to you and should depend on the players you have. I generally go for a Ball Winning Midfielder_Defend alongside a Deep Lying Midfielder_Support but I do change it sometimes to get an Advanced Playmaker in there.
For the front two, you can either have a creative No.10 playing behind a designated goalscorer, such as an Advanced Forward or Poacher (beware the offsides!) or you can go with the Shadow Striker / Deep Lying Forward partnership. I prefer the latter because I like to get the ball wide and put crosses in. But if you have a really creative No.10 who is trained to Try Killer Balls Often and/or is an excellent dribbler, you might want to detail him to provide ammo for your striker.
