The scanner will need to be physically connected to your computer in order for the alpha tag data to be sent to your PC.
Once you have the serial cable, a usb to serial adapter, or the Uniden USB-1, then go into your scanners settings and setup the Serial port.
For the BCD996P2, you can use the USB cable, but you will need the Uniden USB Drivers. Once you have the drivers loaded and installed, connect the scanner to the computer using the USB Cable. The BCD996P2 will connect as a serial port. RadioFeed will then have that port listed as a drop down and you can then send alpha tags from the 996P2 to your live feed.