In this step, you're going to pre-load one of the resistor's pads on the board with solder. This will make it easier to solder the resistor.

Press the iron's tip against one of the solder pads in the outline labeled R4 for a few seconds to heat it.

If you heat the circuit board continuously for more than 10 seconds, the excessive heat may damage the solder pad.

Feed the solder wire into the heated area until there's a small glob of solder on the pad.

The solder should melt onto the pad within a few seconds. If the solder doesn't adhere to the pad, apply flux to the pad or increase the temperature.

Remove the solder wire first, then remove the soldering iron from the pad.