Time for a quick walk through the streets of the city. Go straight on then turn right, taking a left at the end. Go right onto the road where a pickup truck will nearly run you over. Take a left and just head straight into the checkpoint.
Follow the path around to where you'll see the red door through a chainlink fence, you can't reach if from here so continue around to the right then to the left. At the next turn go to the left (the right is just a dead-end with a rickshaw sitting there) and you'll automatically crouch as you move under the tarpaulin and then squeeze under some fencing.
Go right and then around the corner to the left where you'll see your first enemies, go into cover at the sandbags across the middle of the path by pressing Circle. Wait for the soldier to get close enough for you to perform a Stealth Attack with Square. Jump over the sandbags and go down the alley to the left to Stealth Attack the soldier standing with his back to you.
Crouch under the junk in front of you and turn to the right where you'll see the red door again. Go up to it, ignoring the soldiers, and start a Lock Picking mechanic. To solve this you need to rotate the Left Analog Stick until you feel the controller vibrate a little, hold it in that direction until the lock icon flashes green and the first of three sections turns white. Repeat for the other two to open the door.
Head down the steps, don't worry about that light, and you'll see the path split into two directions. The game occasionally lets you choose between different paths that all just end up going to the same place anyway. Going left through the water will take you to some stairs and a door you can creep through while going right will a hole in the floor you can jump up. For the purposes of this walkthrough I'll usually only mention a single path and ignore any alternates.
Going up the stairs and sneaking through the door you'll see a soldier walk past the end of the corridor, quickly make your to him to perform a stealth attack. Go to the left into a room with a yellow wall with a waist high hole in the wall for you to crouch at. Wait for a soldier to walk close so you can stealth attack him to. Hop over the wall and go to the right. You can now go up the stairs to the roof but there is one more soldier around down here so be careful if you feel like exploring.
As you walk through some washing a fighter jet will fly overhead, go to the left.
On some barrels to the left of the ladder, at the end of the washing line.
Once you've picked up the treasure climb up the ladder to where you'll see the Pink Lotus sign, drop down towards it.
Time for a quick melee combat tutorial. Triangle to escape holds, Circle to dodge attacks (with the analog stick), and Square to punch. This is where your difficulty setting is going to actually affect the gameplay as on harder difficulties you won't be able to take as many punches before you die - on Crushing you'll really have to roll out of the way of the punches or you're not going to survive the hold towards the end of the fight just before Nadine jumps in.
Once Nadine arrives make sure to attack the enemy she's attacking to help your buddy takedown statistic if you're going for that Trophy.