Hi @Anonymous ,
Could you show me your error messages?
Could you describe more clearly about what did you do?
I've made a similar test but not met the same problem like your description.
Here's my test:
I click this in the template selections:

Click "create"

Click "Allow"

Then, the app has been created successfully and has no error.
About the send email function, please check the formula in SendConfirmationScreen's OnVisible.

Those formulas decide who the email send to. In the template, the only email address is your email address(_myProfile.UserPrincipalName).
If you want to change it, please refer this:
Office365.SendEmail(inputTo.Text, inputSubject.Text, inputBody.Text)
//inputTo.Text: to email address
inputSubject.Text: email subject
inputBody.Text: email content
If you want to send to multiple email addresses, you could use ";" to connect them.
For example:
Office365.SendEmailV2(_myProfile.UserPrincipalName ; emailaddress2, "Shoutout!", LookUp(Templates, Template="Email").Value, {Importance: "Normal"})
Here's a doc about this connector for your reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/connections/connection-office365-outlook
Bets regards,