The very first thing you need to do is of course to log into your Blogger account which will take you to the Dashboard. You will then need to click on LAYOUT for the relevant blog to which you want to add the widget. Next step is to click "Add a Gadget" (previously "Add a Page Element") in the appropriate section (Header or sidebar or footer or, if you use my template the main column where the posts are). Having done that, you should get a list of (currently) 19 Gadgets (previously called Page Element) like in the screen shot below:
If this is not clear, leave comment and I will see what I can do.