The only way to increase RAM in a computer is to physically add (or change) RAM chips. Not knowing what type of computer you have, it’s hard to say how difficult that would be, but most can be done easily enough by the user. Probably worth it to check your manual, or the computer’s mfg. support website.
8GB is really not enough any more to adequately run a computer these days, especially if you’re running Windows 8 (or worse 10). 16GB RAM is kind of the bare minimum.
