Getting all future emails from a sender to appear in the “Primary” tab (instead of “Promotions”, or elsewhere) is a quick, two-step process.
Open the email message. Click the blue star next to the sender’s name and address to add them to your address book.
Select the From, or Reply-to on an email message, and choose to “Add to Contacts” or “Add to VIPs.” The advantage of “Add to VIPs” is that future emails from this sender will be added to a special VIP mailbox in iOS Mail.