When you've taken care of the three enemies in the courtyard, a cutscene shows a helicopter arriving with reinforcements.
There are 6 more men, but they arrive in pairs. You can fight them from on top of the wall where you've been hiding. Move out and take up a position behind the rubble where you found the ammo and health earlier.
Wait for the first 2 enemies to approach the red barrels at the top of the steps (there's a single barrel on the right and a stack of them on the left).
Shoot the barrel(s) to cause an explosion. Then finish off any stragglers.
Reload by continuing to hold Aim (Right Mouse/Left Trigger) and pressing R/Square/X. If Lara is injured, you'll see blood spatter on the screen and the view will shift to gray/sepia tones. This becomes more pronounced with more serious injuries. Again, to heal, release Aim so she'll duck down behind the rocks. Then press F1 (keyboard) or hold L1/LB and press X/A (controller).
You can continue shooting at the bad guys from here, or if things get too intense, drop down into the area behind the wall to hide and regroup.
There's more rifle ammo behind the forklift...
...and the crates off to the left if you're facing the gate where the enemies enter, as well as plenty of low walls, supply crates, etc., that you can use for cover.
If you're behind cover and have a bad angle...
...you can shoulder swap by pressing Left Shift on the keyboard or clicking the left stick (L3).
You can also zoom in while aiming...
...by pressing Z on the keyboard or clicking the right stick (R3).
If enemies start throwing grenades or Molotovs, a red warning icon will alert you. Scramble away from the incoming explosive as fast as you can or Lara will take heavy damage.
If Lara gets killed and the game reloads, you'll start again in the middle of the area with the forklift and supply crates. Immediately run for cover.
Do your best to kill the first 2 enemies from there.
Then, if you like, you can then retreat to the previous area.
On the way, grab the rifle ammo behind the forklift if you didn't get it already.
Run under the metal walkway into the area with the laptop, and take cover behind the vine-covered wall.
You'll have a good view of the entrance and the wall where enemies might climb over. So you can shoot anyone who approaches. Just wait for them to come to you and pick them off. The main walkthrough also includes a few alternative tactics hat might come in handy.