toshiba's website may have service instructions. also consider the age of the piece. it may not be worth messing with.
Most laptops have hordes of screws (Dell latitude models have 65+ screws in 6 different types) and you have remove many types of them to get to the keyboard. if they are marked in any way, draw circles on a piece of paper. Mark the circles for the screw type (motherboard, keyboard, disk drive, lcd ...). put the screws you remove into the proper circle and don't move the paper until you have completely reassembled the laptop.
Remove the battery, hard drive, optical drive and other loose parts first. Look for notches that show where you can gently pry apart pieces of plastic to access the hardware below.
If they are similar to Dell, there are 4-5 screws marked as KB. Remove those and the bezel piece between keyboard and LCD panel. Carefully lift up the keyboard, noting how it connects to the mainboard. Most use a mylar strip with connectors embedded. You may need to figure out how to unlock the connection in order to remove the strip. Some systems use a 2 part connector. Move one side of the connector and it unlocks. Do not force the connector apart by pulling on the cable. That will ruin the connector.
Reassemble in the reverse order.
As a workaround, try using a regular keyboard plugged into the usb or ps/2 port.