While your soldering iron is heating, put a little liquid flux on each solder "joint". Once iron is hot, take some braid and suck up all the old solder. Using a tiny bit of flux again, apply just enough solder to the pads to make the header stick. Apply pressure and reapply the rest of the solder to final desire.
A comparitively cheap iron is the Weller/Apex WM120. Braid and flux brands shouldn't matter for this (there is only a few available for non-commercial use anyhow).
You can worry about the pins and header orientation, but it's obvious even from the pictures.
The braid will help you get out of mistakes as well. This is all super simple if you've done it a few times...really simple.■