Step 1 - Battery Holder & Switch¶
Flow some solder onto the two battery holder pads near the center of the board as shown in the image below.

Left - perfect pad tinning Right - untinned pad¶
Position the battery holder with the side with the plus symbol facing the switch pads.

Battery holder in position - see the side with the plus symbol faces the switch pads¶
Reflow the solder on the two pads, adding more if necessary.
Insert the switch into the position shown below.
Solder the pins of the switch into place, making sure the switch is flush with the board.
If you are unsure, please refer to the video below
Troubleshooting¶
If solder won’t flow check your iron tip is free from any black oxidation and it has been tinned with solder.
If any copper is showing through the iron plating the tip has worn down and needs to be replaced.
Check your iron temperature is set to 370°C for lead based solder or 390°C for lead-free solder.
Check the solder you are using has a flux core and is ideally lead based.