Step 7: Solder the new jack into place.
Hold the jack in place with a toothpick, popsicle stick, or whatever. Touch the molten solder to the intersection of the jack and one ground pad. If there was flux on the pad, the solder should flow and make the connection. Remove the iron and check your work.
Repeat the process for the other ground pad, then for the signal pad. The rearmost ground pad, which was used for the H.FL connector, doesn't need to be used for the U.FL connector but I soldered it anyway.