Folders are a great way to keep your data structured and enable you to monitor changes more easily.
First you want to determine how you want to view and compare aggregated results (folder view), for example per;

Then you want to build your folder structure accordingly.

Ad a folder via the icon in the top right-hand corner of your results page;

A folder icon will appear on top of your results. Simply type the folder name and click elsewhere on the screen; your folder is saved!

Change the title of your folder via the triangle drop-down, which appears when you hover over the folder;

Email results will not be saved in specific folders automatically. As soon as you see the first data come in, simply move the email to the specific folder (as long as the same Email satisfaction scale is used). You'll only have to do this once per send.
To move an email into a folder, use the triangle drop-down which appears when you hover over the mailing name and then choose 'move to folder';

If you want to move multiple emails into a folder, simply click the emails you want to move. They will turn light blue. You will see a second folder icon appear on the top of your screen. Select to move multiple emails;

Delete a folder via the triangle drop-down which appears when you hover over the mailing name and then choose 'delete'. 

Please note that with deleting a folder, you remove all sub-folders and emails within it!

Select the 'view folder stats' button;

This will generate the cumulative results of all sub-folders and emails within this folder;

Within the folder stats you have the ability to filter on a specific date range and export folder results. 

Scroll down the page to drill down into sub-folders or email stats for a granular understanding of the results;

Managing your results within folders and sub-folders allow you to view and compare data from an overall (high-level) to a detailed perspective. Through the view folder stats button, you'll see the aggregated data. From here drill down, layer by layer to discover best and worst running campaigns and determine your next best step.
Using a folder structure furthermore allows you to set individual KPIs and monitor accordingly.