Help - RTFM - linking articles TO articles

I just installed RTFM and am evaluating some of the features. Right now I
am snagged on one thing:.

Linking articles to articles: in response to “Enter Articles or URIs to
link Articles to. Seperate multiple entries with spaces” I enter integers,
but they only seem to refer to tickets, not articles. What is the secret to
linking an article to another article?