Steps to link sources in an outline:
1. Open the outline.
2. Tap on the topic you would like to Link a source to.
3. Tap on the three dots in the upper right hand corner of Snap and Read.
4. Tap on Link Source.
5. Tap on the box to the left of the source to link it to the topic.
6. Tap on the Arrow in upper left hand corner to go back to the outline.