Reddit reviews HP 8GB DDR4 2400MHz 1.2V SODIMM Notebook Memory [PN: 862398-855]

I'm not sure what led you to buy that specific RAM (perhaps you read the manual incorrectly as they're often generic between several models). The ram you bought is DDR3L, your laptop takes SoDIMM DDR4.

Looking online it seems you have the HP Notebook - 15-bs244wm.
According to this website, it has one slot of RAM available which you can replace the RAM in it with an 8GB stick of ram (possible this one) to get a total of 8GB of RAM.

As for why it looks like there might be a second slot is that manufacturers often make one board to use with many products to save on having to create seperate manufacturing lines, instead just putting different parts on them to create different products.

I see conflicting reports from different sources:

HP knowledge base won't even directly acknowledge the RAM or RAM slots

Brochure says only 1 slot but not user-accessible

The maintenance guide says you need to disassemble it to reach the RAM, although it hints that you could do up to (1x 8GB)

In the end, check to see if you have either two slots, one slot or no slots (I recall some laptops with a soldered RAM.

If you have two slots, then you could use a kit (2x 4GB), like the one you mentioned above.

If you have one slot, you'll need something like this

If you find no slots, you would be SOL, but I don't think that's the case. I think your laptop is user-upgradeable.

As for the Graphics, they're usually not upgradeable.

Good luck!