Normally at this point I'd go to the manufacturer's website, download the manual and find the relevant instruction for you. However Toshiba's website refuses to accept that your model actually exists!
I'm not easily beaten though, so I've just phoned Toshiba's support team to ask them where the 'Source' button is on your remote control. It seems that it's the one labelled with a circle with an arrow through it, underneath the '0' button. Pressing that should bring up the list of sources, so that you can scroll down and accept 'Scart'.