kid cudi :
Ok so can i install a graphics card or what and i do intend to put it on low settings
I'm not in the business of giving advice that I feel will lead to disappointment so I will say that this is against my better judgement.
Anyway, yes you can install a graphics card. However, you're going to be severely limited by the tiny 300 watt power supply (max) included in your computer. I would ask that you take a look at it and find out for certain because I'm going off of a poor spec sheet.
A new power supply would have to be in the 450-500 watt range and also be compatible with your case and components. Almost all retail cases use the ATX formfactor but OEMs such as HP an Dell have a bad habit of using other form factors on some devices. They also have a habit of using custom connectors designed to work only with their own power supplies. This is a form of vendor lock-in. Before you buy anything you will have to verify that it will work.
Here is one power supply that will work. It's cheap but it will do in a pinch:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371045
Here is the one that I would actually recommend for a new budget system. If you think that you might replace the CPU/motherboard/RAM sometime in the next year or so then you can carry this over along with the GPU. I would not recommend that the one above be carried over to a new system. SeaSonic PSUs are worth the extra money
http://www.newegg.com/Product/Product.aspx?Item=N82E16817151074
Here is a good, modern graphics card
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102986
Together those come to $300 and both can be used in a new computer without issue.
As per my previous statement, you'll have to make sure that the PSU will work before you replace it. I also highly advise that you replace the rest of the components as soon as possible.