You can include feeds on your platform by using the rssfeed tag. For the url value you should enter the url of the external feed.

Here are examples on how you can include feeds from yahoo pipes and feedburner:

1. Including feeds, created with Yahoo pipes

Create a pipe (see Yahoo Pipes Tutorials ) and then click on the "Run pipe" link at the top of the page. You will see the feed you just created. Now you should click on the rss icon on the top right of the feed list and select  "Get as RSS" from the drop down menu: