Its quite simple really, imagine the pitch with your goalkeeper on the left. A 4-4-2 formation would then be: 4 Defenders, 4 Midfielders and 2 Strikers.

More complex formations involve Defensive midfielders (DML, DMC, DMR) these sit between midfielders and the defenders and Attacking Midfielders (AML, AMC, AMR) these sit between the midfielders and the strikers.

So a 4-1-2-1-2 formation would be: 4 Defenders, 1 Defensive Midfielder, 2 Midfielders, 1 Attacking Midfielder and 2 Strikers.