You need a flatbed film scanner, this is the basic type. It has light on the lid which will shine through the film and scan the negatives into the computer.
There is also drum type scanner but a lot more expensive.
Another DIY method is using a normal scanner and a phone or light box to light up the negatives and scanning it. It's a bit more time consuming I guess.
Also, there is the lomography smartphone scanner, using the camera of smartphones to "scan" the images. Google it.