You cannot change the graphics card as the HD 4400 graphics are integrated with the processor.
However, since your machine is PC and not a laptop, if you have an available PCIe x16 slot, you can add a card that is compatible with the motherboard and slot, and compatible with the OS. Make sure you understand what "compatible" is. Many manufacturerss will claim compatibility, or backward compatibility, and may not actually be compatible.
Best thing to do is to check the specifications on the motherboard for the PCIe x16 slot, and look for tested cards or cards known to be compatible.
Also, when inserting a graphics card, it will typically disable the onboard (integrated) graphics. So, you will likely not have both add-on graphics and integrated graphics.
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