Can my pc get a graphics upgrade?

Without looking into the computer more, it looks like you are using integrated graphics, meaning most of the time you can't get a graphics card due to no PCI-Express slot - but I could be wrong so please check!

The PSU is also hightly required and with most pre-built machines, you will find that you will have a low PSU wattage and therefore can't buy much graphics cards without upgrading your PSU.

Personally, check your components and do the following -

Check PSU wattage - If the PSU is around 500w, you'll be fine. If this is any lower, you may need to upgrade this!

Check PSI-Express slot on motherboard - If this doesn't have a PSI-Express slot, you'll need to buy a new motherboard (most probably a MATX).

Check if the case can support your graphics upgrade - Most cases like these aren't made for any GPU's (or long GPU's) to be added. This may need a new case upgrade.

According to the website it doesn't have any expansion slots, if so you can't upgrade it

It can, but it depends on what Graphics card you want in it.