Q: It said that I got stamps / tokens. What are those?
Stamps and tokens are basically another kind of currency. When you get enough of them, you can trade them in for an object (such as a bear or a building).
Q: How do I know how many stamps / tokens I have? How do I redeem them?
Go to the appropriate building where stamps / tokens are redeemed. These include the Post Office and Planning Dept--there is a different building for each kind of stamp / token. If you stand on the building then you'll be able to see the number of stamps / tokens you've collected and how many you need for your next reward. If you have enough, you'll be given the option to redeem them.
Q: I don't have a Post Office and/or Planning Dept!
You'll get one when you get the first stamps/tokens that are redeemable at that particular building.