To schedule when a campaign will send emails, switch to the Schedule panel:
From here you can define Send Windows, which are periods of time when campaign emails will be eligible to send.
You can turn off sending for certain days, or modify the start/end times
One thing to note: email sending is not evenly distributed throughout the window. Once a window is open, the system will try to send as many as possible until it's finished or hits a limit. So practically speaking, most of the emails will generally be send close to the start time.