You don't need to take the laptop apart. There is a memory expansion slot accessible by removing a small panel on the bottom of your laptop.
Turn the thing off, take the two screws out, lift the plastic cover off, slide, the new memory module into the slot, put the cover back in place, put the screws back in and turn it on.
Detailed directions can be found on Toshiba's WWW site:
http://www.toshiba.com Use their "Ask Iris" feature in Product Support and ask the question "How do I install Memory?"