Only showing titles – how to show posts in rss feed?

As ypu can see at http://vintagemaniacbloggen.net/ I’m using fetch_rss to show a feed for another blog of mine, but I’m only getting the titles for the posts – I want to show the posts in the feed(or an excerpt, doesn’t matter which).

How do I get a feed to show the posts it’s linking to?

(I’ve never dealt with rss feeds before, so excuse me if I’m asking a stupid question)