You can "upgrade" the integrated Radeon HD 7640g by replacing the A8-4500m APU with the A10-4600m APU which has the slightly faster Radeon HD 7660g. The HD 7660g has 128 more shaders and the graphics core is 31MHz faster; 384 shaders / 686MHz. The performance increase will be slight, but there is a performance increase.
The laptop was probably advertised as "discrete like" graphics performance. There will be no way to install a graphics card / chip. Only specific gaming laptop models gives you the ability to upgrade the graphic card and those laptops start at $1,500; if not more.