Arduino Nano (3.0) Use an USB Bluetooth stick
Interfacing an Arduino with USB is already VERY hard. USB does not use the same Serial as protocol so don't connect it to Tx and Rx. The only way to interface an Arduino and an USB device is trough a USB shield, which is quite complex already.

Just for you information. USB uses 5V so no voltage divider is needed to reduce it to 3.3V. A voltage divider is pretty much 2 resistors in series where the original voltage goes in one end, the output voltages is between the 2 resistors and the other end is connected to ground. Read more about them here.

Now, communicating with Bluetooth is also complicated, but mix USB + Bluetooth and you get something ALMOST impossible (I hope the ALMOST is clear enough for any hatters). It is possible, but seeing you level of knowlage, simply don't risk having a severe depression trying to fingure it out!

In the end of the day, your plan of using that Bluetooth USB module is just going to be crazy complicated and big.

A more effective solution would be to use a module such as the HC-05 Bluetooth module. It is quite cheap if you get it from sites such as Amazon. Link here for this product on Amazon.com. It is designed with the Arduino in mind thus making programming easier. You project could also be a little smaller, because this module pretty much has the size of your Arduino Nano.

Hope it was helpful!