When setting up the Arduino IDE, have your Arduino or compatible board and the USB cable at hand. Installation of the required drivers should occur automatically if you have the board plugged into the computer when you install the software.
Go to the Arduino downloads page and download the correct installer file for your device as shown in the image below.
When you open the Arduino IDE and click on the Tools menu, you should be able to see an option titled "Port" and it should be black and clickable. If it is greyed out and unable to be clicked, you will need to separately install the drivers for the Arduino board. They can be downloaded from the links on the LittleBird KnockOffDuino page. Alternately you can follow the instructions linked here.