simply: you can't upgrade an integrated gpu.
the integrated gpu is usually built into the processor. on in older systems, a chip on the motherboard. it cannot be removed or changed. you can only enable/disable it and change a few settings.
you can, however, upgrade
to a better gfx card if you're using desktop pc and if your pc's motherboard has a slot to fit the gfx card. in some laptops, you can add/change the gfx card.
you can run a monitoring program like piriform's speccy or techpowerup's gpu-z to determine what gfx chip (integrated or otherwise) your pc is running. it depends on your system specs.
speccy:
http://www.piriform.com/speccy
gpu z:
http://www.techpowerup.com/