To set your newsletter send schedule, go to Schedule → 
Settings. Once on the Settings page, you will have the ability to choose the frequency of your newsletter, which day(s) of the week your newsletter sends, what time you would like your newsletter delivered to your contacts, what day you would like to start sending your newsletter (for the very first time) and the content review cut-off time.
The content review cut-off time is the review window you can set for yourself to review your upcoming newsletter. During this review window, you can view articles for your upcoming newsletter and toggle any articles off that you may want to take out, you can manually add an article that you may have found to include, and do any updates to the design before send. Once the cut-off time is set, new articles will stop coming into the upcoming articles pool.
The review time should be input as a # of hours before send.
Your newsletter will not start sending until you set a start date.