Click on the "Feedback" tab (1) to request feedback (2).
You can choose which peers you want to ask for feedback. The only limit is the number of possible requests: this is defined by the campaign owner. An overview of the questions asked is shown below.
Select the desired peers: notifications are sent to them, and a new "Requested Feedback" tab appears in their Poplee Performance interface.
You can follow the progress of your requests from the review.