How to Add an RSS Widget to Your WordPress.com Blog
The RSS widget lets you display content from another blog in the sidebar of your WordPress.com blog. If you want to display a list of recent posts from another blog that you have somewhere else, for example, you can use the RSS widget to accomplish this task.
Add the RSS widget to your selected Widget Area on the Widgets page.
All the widgets are listed in the Available Widgets section.
Click the drop-down arrow to the right of the RSS widget's name.
A box drops down, displaying the different options you can configure for the RSS widget.
In the Enter the RSS URL Here text box, type the RSS URL of the blog you want to add.
Type the title of the RSS widget.
This title is what will appear in your blog above the links from this blog. If I wanted to add the RSS feed from my personal blog, for example, I would type Lisa Sabin-Wilson’s blog.
Select the number of items to display.
The drop-down menu here gives you a choice of 1–20. Select the number of items from the RSS feed that you would like displayed on your site.
(Optional) Select the Display the Item Content box.
(Optional) Select the Display Item Author, If Available box.
Select this option if you want to display the author’s name along with the item's title.
(Optional) Select the Display Item Date box.
Select this option if you want to display the date the item was published, along with the item title.
Click the Save Changes button.
WordPress saves all the options you’ve just set and reloads the Widgets page with your RSS widget intact. You can now display content from another blog in your sidebar.