At the following link Drivers & Software you will be able to find the drivers available for your motherboard.
Bear in mind that whenever you add a graphics card to the motherboard it will disable the Intel graphics unless you have a feature in the BIOS that can provide you to choose between them, note the picture below:
For further reference Multiple Displays Frequently Asked Questions (FAQ) for Graphics....
For the HD5450 card itself, you need to load the appropriate AMD driver. A version of this driver is usually provided on a CD (or DVD) that was packaged with the board. Alternately, you can download their latest driver from the AMD website.