We will line up as shown in the first diagram. We'll play a 2-3-1 formation, but I'd like us to think of it as a 2-1-2-1 formation with the CM playing lower than other mids as a kind of controlling/defensive midfielder.

When we attack, as diagrammed, our right and left midfielders will get pretty high to play with the striker. The CM should remember to remain lower to be able to pass deep and wide to midfielders,  provide back pass support and be the first defender when the ball is turned over in transition. The ball side defender (RB in this instance) should also play pretty high so that we do not allow the other team to build up momentum when coming back into attack. 

In defense, the ball side defender (again, the RB in this case) will press the ball while the other back (LB) provides cover for them. The CM assists the LB in that cover while the RM and LM balance the field and mark players. The ST remains relatively high so we can quickly counter.