Step by step Tutorial on how To add A Gadgetin Blogger.
Also there are Some Basic tips in navigating in Gadgets section.
Step 1: Go to Blogger>Layout>Page Element
Step 2: Click "Add a Gadget". Where you want to place the Gadget.
Step 3: You will see a List of Gadgets there. Try out some. Try to go to the most popular gadgets category. There you will see the most used by widgets by other Bloggers.
There you have it.