Standard templates are predefined templates for newsletters, that you may use directly. The title of the included standard templates begins – who wonders – with standard. They all are responsive. That means, that they look well even on small displays, which occurs on mobile devices. Nevertheless standard templates can be individualized widely. To keep out of harm's way I suggest to copy a provided template and then adjust. If an adjustment is not possible with one provided template: Perhaps it is possible with another?
At the left you make the adjustments, at the right you see a preview of the template, that will be refreshed by clicking to Refresh preview. A refresh also will be done, if the template will be saved.
Here you do the general settings to the template. The template gets a name and a description, you set the width of the newsletter as also the font size, the space and the colour for font and background of the various sections. Here you also may select a little image, a so called thumbnail. This image is shown in the list of the templates as preview and in the tool-tip at the select list, if you create a newsletter.
This preview image is not identically to the preview at editing a template! The preview while editing is dynamically and can be refreshed again and again, while the thumbnail is a static image, in example created with a screenshot.
This preview image is not created automatically by BwPostman! You can create such a preview image, if you take a screenshot of the newsletter. You quite may take the screenshot from the preview while editing the template. BwPostman looks for preview images in the folder <Joomla-installation-directory>/images/bw_postman. Here you have to upload the saved image. Uploading you can do with Media Manager if Joomla!®, which you will find at Content → Media Manager.