Here is an example of what you will see in the "Ad Sets" page of a campaign:
To start with, you can add new ad sets by clicking on the "New Ad Set" button. For the already live ad sets, the "Active" button means that the ad set is activated and is currently running. From that button we can activate paused ad sets, pause active ones and also delete them. "Delivering" means that the ad set is bringing enough conversions. If the ad set is not delivering, you can hover over the "Not Delivering" status and see the reason why it's not delivering.
Since the "Potential Reach" information comes from FB, with the last changes the information can't be obtained and just in some cases it shows the estimated reach. Details like the audience (included and excluded), location, age, gender, interest & behavior groups and placements can be seen when you scroll down the ad set's box.
Settings section in the second box of the ad set is where you can set the Budget, Bid and Scheduling information of the ad set. It's not clickable for the campaigns with Marvin as Marvin does the allocations. For campaigns without Marvin, the budget, bid and schedule of the campaign can be seen in that part of the ad set.
On the last box of the ad set, you can see the assigned creatives and add or discard them. If you pause the ad set, the assigned creatives will be discarded automatically.
To manage the ad sets and make modifications on them, you need to click on the "Edit" button. This will open a pop-up window that will kind of remind you the campaign creation process.
All of the ad sets that are included in the campaign are listed in the right column. Next to the ad set names, you can see the "Mark as Favorite", "Clone" and "Delete" options as icons. If you mark the ad set as favorite, you can see the ad set at the top of the list when you click on the "Load from Library" button, it becomes more accessible. Under the name of the ad set you can see the potential reach and the specified targeting options for each one.
One of the most significant functions on this page is the "Bulk Edit" option which is placed on the top of ad sets.
Once you click on this button, you will see a pop-up window where you can apply your ad set edits in bulk.
You can apply your bulk edits in 10 categories to your existing ad sets as seen above. You can also choose the "Bulk Edit" option in the Ad Sets page from the "Actions" button next to the "New Ad Set" button, besides Assign Creatives, Delete and Pause options.
The other important point is that, after applying any changes to your ad sets, you need to click on "Budget" button at the bottom of the page. Keep in mind that you need to continue till the end of the process by following the path (Budget > Assign Creatives > Save Assignments) in order to make sure that your changes are live.