The Save button is located at the bottom of the Engagement Details page. Once you have entered the minimum information to create an engagement (Administrator only - Engagement Name and Engagement Dates), you can save the engagement.
Any Administrators and team members assigned to this Engagement can now add/edit content and save at any time by clicking the Save button at the bottom of the page.
Please note: clicking the Preview button also saves all the new/edited content on the page.