The content tab within each campaign is where you'll find individual branded posts for each campaign.
Using the filter at the top, you'll be able to see branded content by platform sorted by important metrics unique to each platform. For example, if you wanted to know which piece of content had the best engagement rate on Instagram, you would select Instagram as your platform, then engagement rate as your sort-by*.
You're then able to click into an individual piece of content to view in-depth stats, time-series data, and in most cases, how the post is performing against that creators averages.
*Occasionally, there is no data available to display for some filters, such as impressions for content posted by creators without Instagram Business. This content will be sorted at the bottom of the list.