By default, there are no rules set for a new promotion. To show a tab, you'll have to go in and add it as a rule.
1. Once you enter the promotion you'd like to edit, click on "Promotion Rules"
2. Here you will find rule options you can add to your promotion. To show your tab, click on "Add" under "Show Tab". Follow the instructions on next page to edit additional conditions. Click OK.
3. The rule will be added to your rules list. Hit "Save" and then "Publish" to finalize the promotion!