You render it.
If you replaced a clip in PrPro timeline with a dynamically linked composition, you don't need to perform any extra steps to get edited footage back - it's already there: when you make changes within your dynamically linked composition inside of AE, PrPro automatically updates them in its timeline.
So as to get smooth playback in PrPro you need to render preview in most cases. If rendering preview takes too long, it is wise to render digital intermediate out of AE, as Mylanium said, reimport it into PrPro and utilise instead of dynamically linked comp.
The problem is that the video i saw from the "product evangelist" for adobe made a big deal out of not needing to render. Is there a difference between rendering in the general sense and rendering an "intermediate" or "preview"?
The purpose of Dynamic Link is to eliminate rendering step while sharing assets between e.g. PrPro and AE, i.e. you don't need to render your footage out of AE and reimport it into PrPro every time you make change in the linked composition within AE.
Rendering preview within PrPro deals with those yellow and red bars on top of the timeline. If your machine can't playback yellow and red sections of your timeline smoothly, you need to render preview (green bars indicates sections with rendered preview).
However if you have quite complex After Effects composition, rendering preview in PrPro may take ages. In that case you'd rather render intermediate with lossless codec out of AE (you may also see this thread in PrPro Forum with advanced comments from Todd about Dynamic Link workflow).