1) Make sure that you are logged into your blogger account
2) Now click on the widget installer button below.
3) In the new Pop up page fill in the details and click the customize button
4) When filling in the url dont use http:// and dont use a slash at the end of the url.These are automatically added by the widget installer.
5) A new page will open up.In that New Page Opt to save the widget
6) Now you will be taken to the Blogger Page Elements Page
7) You can drag the newly installed widget to the position which you want.