Step 1: Go to "www.gogole.com"
Step 2: Open "Bloger" and "adsense" site in two tabs
Step 3: Sign in with your google account
Step 4: Select "My ads" in left pane
Step 5: Select "New ad unit"
Step 6: Enter name, ad size and ad type as your wish
Step 7: Select "Save and get code" button
Step 8: Now copy the code generated
Step 9: Now go to blogger admin page
Step 10: Go to "Layout" in left pane
Step 11: Go to Sidebar and click "Add a gadget"
Step 12:Click Add widget button in "HTML/JavaScript"
Step 13:Leave "Title" as blank
Step 14:Under content Paste the code you copied
Step 15:Now remove the text "ca-pub-" and the next line code
Step 16:Click on "Save" button
Step 17:Now go to your blog and refresh (F5 Button)
Step 18:Find your add, You Done!