You just need to open up the case then looks for the main board. Should be obvious, it's the one everything plugs into.
Then towards the back then will be looks of silver blanking plates which each (or there abouts) have a slot 3 or 4 inches long leading up to them.
One will be longer and set back a little further than the others.
Where this one says "AGP" yours will be a PCIe slot
Then you match the card up to the slot, take off the blanking plate at the back. Push the card in carfeully but firmly until it's level and it's own bracket lines up where the blanking bracket was. Screw it in.
Now since you have intergrated gfx you may need to turn that off in the bios. But I would test the water first.
So unplug you current monitor cable and stick it into the new card and turn on.
The drivers for the card will be in the box, install in windows. Done.