Hi Udenk,

If you want the Motherboard to be the receiver then choose the HC-06. This will enable you to send data to the Motherboard via Bluetooth. Controlling the Motherboard with your phone for example. If you need it to send and receive data, then choose the HC-05. This would allow the Motherboard to control/send data to another Bluetooth device and receive data.

Here are some links for your country:

HC-06: https://www.ebay.com/itm/234062601071?hash=item367f37db6f:g:tl4AAOSw~N9hdfKy
HC-05: https://www.ebay.com/itm/192001699774?epid=1195807318&hash=item2cb4316fbe:g:FDUAAOSwZJBYB4ZM

They should work just by plugging the module into the socket on the board. I have tested it a fair bit and had no problems. But, to be on the safe side, add a 20k (or two 10k in series if they are on hand) between the Rx and GND pins of the Bluetooth module socket (on the back of the board). This will act as a voltage divider with the 10k resister already present on the line connecting Rx on the Bluetooth to Tx on the microcontroller. This lowers the ATMega’s 5V logic down to the 3.3V the Bluetooth module is rated for.

Hope this helps,

Martyn