Before you start I strongly recommend that you start with the "Fat Pika" board.  The bag containing Fat Pika also contains the Resistors used for both boards and since the LEDs are not marked you will mix them up if you unbag them both!    Of course you can always just take the resistors out of the bag but for the sake of argument I'm assuming you're planning to assemble both boards anyway so you might as well start with the one that has everything you need in 1 bag.

If you are assembling this kit I assume you have done some amount of soldering in your life, as such this guide will not be very hand holdy.  The instructions are the same for both boards, other than LED color they are identical in how your assemble them.

Also Note: There are 4x Resistors with the kit, you only actually need 2 but they're so small I included twice as many as you should need in case you lose one while assembling it.

Start by adding a fair amount of solder to one of the pads for each of the LEDs on the board.  I usually do it on the "-" symbol but it doesn't actually matter.

Place the LED Upside down so that the top transparent lens is facing into the board, then while holding the LED with tweezers you can bridge the solder onto the end of the LED.   Once you have secured one side, you can do the other more easily.

This picture will show you what it should look like.

Once you've soldered both LEDs place the 2x2 Header on the board and solder it into place.   The longer pins should be on the bottom and the short should be poking through the top.  I recommend using clamping tweezers if you have them to make this part easier.

Once you've finished soldering the parts onto the SAO Reject board you can move on to to the SAO Fix Board.  The SAO fix board is simply another header and a resistor. 

First solder the 0805 resistor to the board.

Once that's completed solder the second 2x2 Header to the SAO Fix board.  The header should be soldered so that the longer pins are on the BOTTOM where it says "SAO Fix v1.0".

Once you've assembled both the Add-on and the SAO Fix board now you can attach them.   Simply place the Badge through the side of the board labeled "Add-on" so that at the bottom "Badge" is visible and solder the headers into place.

Once you've finished soldering the boards together use wire snips to remove the 4 pins up to the point where the solder is.  The mechanical bond should be strong enough to hold everything together.

After that's done test it on a 3.3v power source and you're good to go!