|Your graphics are integrated onto the motherboard and can't be upgraded.|
All you can do is share more RAM to the graphics. That is a setting in the BIOS (setup) screens. The amount you can share is determined by the amount of installed RAM and the limitations of the graphics chip. Below is an excerpt from the link you provided.
* ATI Mobility Radeon HD 3100 Graphics.
* Up to 1279 MB total video memory using HyperMemory.
The 1279 total video memory is the most you can share. There may some memory on the graphics chip that is dedicated and you can share more.
Read your manual for more information on that topic.