Send email to a definite number of customer each week automatically

Send email to a definite number of customer each week automatically

Hi everyone, 
I have just started with Zoho ecosystem as a part of my job. And my newest task is to send mail to 12 different customers every week automatically, no duplicate customers every week, so how can I use Zoho Flow to pick out 12 customers' emails out of the Zoho Sheet and then send mails to them every week automatically? I'm struggled with it every single time, I would be so appreciated if you can lend me a hand. Thank you for reading this.