The memory on Toshiba Tecras (if I'm not mistaken) is installed on the bottom of the laptop. Most laptops are made like this, coincidentally.

Your Tecra should have no problem accepting 128mb modules, although 256mb will probably not work.

The Tecras I've seen also have 2 slots and usually come with 1 module of 64mb of memory, standard issue. They are probably labeled A and B, but I'm not that observant. There are two slots though, so that is probably the right place.

Each slot should be notched so only memory can fit in. I foudn this picture to help you out (not the same laptop).
http://a.r.tv.com/cnet.1d/i/co/laptoptips/memslotnb.gif

 

I must have added 128mb of ram to mine, because I now have 192mb.

I bought the ram chip from Toshiba.

It was pretty simple to install, I belive I just put the 128 chip in the second slot.