Need to enter BIOS and see what is the maximum amount of System RAM you can assign to your APU Processor.
You can increase it to at least 2GB or maybe 3GBs depending how much BIOS will allow you to allot to the APU from System RAM.
Generally 512 MB of RAM is the minimum amount of RAM that can be assigned to a APU via BIOS.
Otherwise you will need to install a separate GPU Card to get more vRAM for your games.
EDIT: If you should be talking about a Laptop APU then if BIOS doesn't have a setting to increase or decrease the vRAM on the APU then you are stuck with whatever amount the APU has assigned.
Not all laptop allow you to increase or decrease the amount of vRAM assigned to your APU Integrated Graphics.