Hello @KayL53 ,
If you need to manually do a resend to non-openers after an email's been sent, there's a couple ways to go about it.
The first and easiest would be to go to the email's Did Not Open report numbers, select everyone, and do a Quicksend. This can only be done if there's 500 or less contacts being selected.
The other method would be to make a list from the report, then copy the email and send that copy to the newly made DNO list.