If you're unable to find the New or Edit buttons, it's likely because your Salesforce user does not have the "Marketing User" option enabled. Here's the steps you need to follow to enable the Marketing User option for a user in Salesforce.
1) Go to Setup > Administration Setup > Manage Users > Users > Edit (the selected user) > Marketing User checkbox: check this checkbox.
2) Click the Save button
That's it! Happy emailing!