After logging, you will find the following page and click on Settings on that page.
A new page will be opened and here you will find a option mentioning You can also add Twitter to your site. Click on it.
Now, display updates on your web page will be opened. Click on Blogger and then click on Continue to go to the next step.
This is the page where you can set all of the Twitter settings. Select the No of updates to display, title of your Twitter widget and finally click on Blogger icon.
Log in, to your blogger account and then select your blog and Title. At last, click on Add Widget.
Now, you will see that the widget (Twitter Widget) is automatically added to your blogger blog. And that's all to add or install Twitter widget into your blog. I think, you have done successfully.
From now, you will see that all of your message will be displayed on your Twitter widget.