Hey,
To add the alternative text in the pictures, you can follow these steps:
1. Double click in the content section where you want to add an image-> Editor tab will open.
2. Editor tab-> Click on Image, a Picture dialog box opens.
3. You will see the Alt Tag option there.
To add the Caption HTML to pictures and alternate text & Caption HTML to elements, you can directly add the Custom HTML code in the content section in TemplateToaster.
Simply, Double click in the content section-> Paste the custom HTML code directly.