Enable status means that the template is available for all users to send out to existing clients/prospects and is also available to be published online.
Disabled status means that the template is not available for all users to be sent out to existing clients/prospects and is not available for online publishing.
To change the status of a template go Templates > My Templates under Form Templates and click on a Template. Click on the edit button.
There will be a status radio button where you can choose to either have the template disabled or enabled.
Once you've made your selection click on the green Save Changes button.