Electronic – arduino – Identify capacitors in Arduino Starter Kit

Looking at the link, it seems this is intended as a prototyping board that is compatible with Arduino.

If this is the case, then there are no need for schematics or assembly instructions as they do not know what you will want to use it for, that is you decide on it's function/circuit.
I suppose there could be some documentation with ideas to try, like a circuit cookbook, but they would not have to be associated particularly with this board.
This is similar to stripboard, or breadboard - the idea of these coming with schematics or assembly instructions doesn't make much sense.

Once you have prototyped your circuit you could have a board made, and set the idea "in stone" (i.e. the board can only be used for that purpose and would need assembly instruction and schematic)

The problem with the relays isn't that of current, but of voltage. You will need to supply 12V to the coil of those relays in order to get it to energize.

One option is to find relays that only require either 5V or 9V instead, so that it can be either powered from the Arduino's supply or from a 9V battery. You will still need the transistor if using 5V relays, since at that point the coil will need more current than the Arduino output driver can provide.

Another option is to draw power from the incoming AC line and put it through a regulator to get the 12V required to operate the relay. Additionally, a 5V regulator will get you the power you need for the Arduino so that the entire apparatus is powered off the line.