You probably need to head to the manufacturers/brand website, there should be a register warranty option/link somewhere in the support section. Google your computer model to find out the manufacturers name if you don't know, alternatively you could call your retailer to find out.
you not get papers with it, giving you the web site. What you need to do is see what make it is, then find the official website.
For example, if mine was a Toshiba, I would type into google, ......Toshiba official web site......It will then take you to the official website and somewhere on it it will give you the option to register your laptop.
For example, if mine was a Toshiba, I would type into google, ......Toshiba official web site......It will then take you to the official website and somewhere on it it will give you the option to register your laptop.