Submissions
When a writer submits a draft for review to a publication you own or edit, you'll receive a notification in the site menu and by email (if you have emails enabled).
By email:
In the body of the email notification, click on "View draft" to review just this one draft (see Review Submission for more), or "View all submissions" to see all pending submissions.

Via the site menu:
Go to your publication's home page, and click on the down-arrow next to the "Follow" button:

From the drop-down menu that appears, click on "Submissions".
Manage Submissions
From your submissions page, you can click on any draft title that appears in your submissions list to manage it:

This will take you to an editable draft of the submitted story, which editors will be able to review, make changes and publish.