Some users might find that they can't create a new Soapbox Mailer campaign because, well, they don't see a New button when they click on the Campaign tab in Salesforce. Soapbox Mailer doesn't limit access to the app to individual users or profiles. Instead, Soapbox Mailer is an organization-wide license. Typically, the reason why a user might not see a New button on the Campaign tab is because their user isn't a Marketing User in Salesforce. Here's how to change that.
1) Go to Setup > Manage Users > Users
2) Click on the name of the user you wish to give marketing rights
3) On the user's page, click the Edit button
4) Check the Marketing User checkbox
5) Click the Save button
6) Confirm that the user can now see the New button on the Campaign tab