Log into your own personal Gmail account
Left Click on Compose which is located on the top left hand corner of your Gmail screen.
A new window will pop-up like this
Look for the down arrow that is right beside the send button.
Left click on Schedule Send.
A new window will come up that looks like this. Pick your date and time you want to send the email and Click Send.
If you want to see a video on it, it can be found below.
YOU ARE DONE!