If you want to try and do it yourself, here is a sample list of graphics cards you can add to your Desktop computer:
http://www.newegg.com/Desktop-Graphics-Cards/SubCategory/ID-48
Familiarize yourself by first turning off your computer.
Unplug the power cord from the power supply and open the computer to have a look inside.
It's actually a neat process to do it yourself if you want to. (also saves you money.)
Better yet- get a friend, family member or neighbor who is tech savvy to do it for you and watch how they do it.
Once you plug in the new graphics card and turn on your computer, Windows will automatically find it and install some drivers for it. Then you just head on over to the manufacturer's website and download the latest driver for the card, install and you are golden.
For the money I would recommend either this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121686
Only one thing you should note:
Make sure your Computer Monitor has an HDMI or DVI or Display Port connection ! before you upgrade your video card ... some newer graphics cards do not plug into the older VGA port. So double check your monitor input connections.
Rob
PD 14 Ultimate Suite / Win10 Pro x64
1. Gigabyte Brix PRO / i7-4770R Intel Iris Pro 5200 / 16 GB / 1 TB SSD
2. Lenovo X230T / 8GB / Intel HD4000 + ViDock 4 Plus & ASUS Nvidia 660 Ti / Link: https://www.youtube.com/watch?v=ZIZw3GPwKMo&feature=youtu.be