Got this link from the web.

http://www.gardenguides.com/119-starting-tuberous-begonias-off-right.html

Remember to plant the concave side up. 3 inches is about right. You can start them inside if you have a nice sunny spot. They do grow big and quite fast. Now is probably a good time to start in Ontario. It's always iffy with the weather here. Last frost date is around May 24, but I usually have my plants out weeks before that. Your begonias will have a good head start if you plant them now.

Thanks for the link mikey33. I planted them up right after I bought them. The 'tuber' that was in the pkg looks more like a large gladioli corm except that it is about 1/2" thick. I did plant as suggested and now I'm just wating for signs of growth. Thanks.