Go online, go to bill pay, enter the new payee name and deposit info that you receive from the Mortgage Co. Set the date you want the transfer payment to show up in the Mortgage Co's. account each month and the task is complete. All you have to do after that is make sure there are sufficient funds available upon that date.
You need to contact your bank about starting a monthly direct withdraw from you bank account. If you have an online account, then you can ask them to set it up for you so that your financial transaction can be easier.