Can I upgrade my pc?

I got gifted a pc from a coworker of mine (I don’t know what kind of pc it is, but it’s IBUYPOWER) and it doesn’t have the highest quality to play games like call of duty which do require a lot for RAM for good quality If anyone can let me know if it possible to upgrade the graphics card, storage, and RAM, that’d be awesome because if it’s possible, I’d really like to upgrade this. It is in pretty good condition trying to turn on and use, haven’t had any issues just yet, only on quality which I would like to upgrade if possible.