Okay, so you finally start the game, but you need to be trained before going into battle. A sergeant and a private will welcome you, and you will be ordered to run. When the sergeant finishes, hold 
to start moving, then double-tap it to sprint all the way to the wall. Do not run towards him, just to the wall and keep going until it says "Objective Complete."
Next you will have to go to the obstacle course. Just walk out of the building, immediately make a left, and keep going until you get there. After you receive your orders, go to the logs and tap the mantle arrow. Then go to the bridge, tap the arrow again, and walk all the way. Do not turn, or you will lose your balance. Next double tap the down arrow to crouch, and go all the way. Double tap down to stand up. Just keep moving and you will climb up.
After you report to the private, make a right and follow the path to a sergeant. You will have to walk to the guns, and touch the sign up top to pick up the Thompson Sub-machine gun. Walk to where the guys were before, and shoot three targets. You aim by moving 
around the green area until the crosshair is where you want it. Press 
or 
to shoot. Then double tap down to crouch and shoot 3 more targets. Get up, and pick up the M1 Rifle. Go back to the shooting line, press the circle at the top of the touch screen to go into Aim Down Sight Mode. Shoot three targets. Go back, pick up the Springfield Sniper, press the same circle, and take down another three targets.
When the sergeant finishes talking, walk up to the grenades and you will automatically obtain them. Touch them on the screen, and they should be in your hand. Move the crosshair to the windows and doorway and press or to throw them. Next you will pick up the 30 Cal Emplacement, touch the hand at the glowing holder. Shoot three more targets. Pick up the M1 again and shoot anywhere once. Then walk over to the box, and you will see that your ammo has been resupplied.
Finally, you walk in and out of the building behind the sergeant. Go to one of the mortars and touch the hand. Move the left wheel all the way and the right wheel to get the mortar in front of the oval shaped target. Press or to blow it up and do the same with the other. Press the hand and walk back up. The sergeant will say words you need to remember: "Remember what you've learned here, keep your wits about you, and do your country proud." You are now ready to fight in the next level!