You can use Personal Invites to send an invitation to a list of recipients (or to a single person) which will give them access to a specific Pricing Group. Using Personal Invites allows you to keep your registration open to those without invites but give special access to certain people. When someone receives a personal invite they simply have to click on the link in the email and they'll be taken directly into the Pricing Group specified in the email blast (they will not have to enter a promo code).
To create a Personal Invite navigate to the Messaging tab. Next, select the Personal Invites button under the New Blast heading.
Next, add a subject line and create the invite. Once you've created the invite select the Pricing Group the recipients should have access to.
To complete the set up, simply draft an email and upload recipients the way you would with any other email blast.