I take it that you are clicking the "send" button on this screen?
This button performs a script. When I examine the script briefly, I find that send mail step inside this script does not have the "perform without dialog" option selected. I believe changing this option will result in the emails being sent without your having to click send on every email. Whether this is a good option for this starter solution and script, you'll need to test and see if it works for you.
The script is named "send campaign" (I found this out by double-clicking the button hidden behind two other layout objects) and is located inside the Action folder inside the campaigns folder you'll find when you open up Manage Scripts. Learning how scripts work and how to modify them is a key skill to learn if you want to create and/or modify your own FileMaker solutions.
Thanks I will