You can always check the status of the form on the Form list view. There on the Status column, you'll see Published, Unpublished or Draft status.
For publishing a form you can click on the play button, this will make the form url publicly accessible.
If you wish to un-publish the form you can click on the pause button. This will make the form url return a 404 code and the preview mode will be active only for logged in users.
3. Change Form state via form settings
You can also edit the form status via the form settings as follows: