If it's only got an Intel GPU with no switchable graphics, you cannot upgrade it.
Even if it does have a discrete card for switchable graphics, there is no guarantee that a different discrete card will actually work.
The only feasible upgrades on a laptop are usually the RAM & the hard drive, that's why it's especially important to make sure any laptop you buy has the graphics & processing power that you are likely to need, both now and in the years ahead.