Unfortunately, there's currently no way to link specific sources to specific events (in the name, birth, death, marriage fields, for example), but there's a great way to cite sources in the narrative.
As you're typing the narrative, you can use the REF /REF tags to insert footnotes. For example, you'd type:
John Patrick Smith was born 17 March 1882 in Buffalo, Erie, New York.<ref>St. Peters German Evangelical Church, Births 1882, page 2, FHL Film #1317892</ref>
The REF tags then generate footnotes at the bottom of the narrative as long as there is a tag near the end that looks like this: <references />