Hello Agrimagweb,
Thanks for reaching out to us.
We apologize to say that there is no API support for the attachments.
There is only one option to import the attachments by CSV file but that feature does not available in a light version.
Like, Attachment Name; SKU; Attachment URL
In the above format if you have a list of 100 or more products then it will one-click import all the attachments according to the mentioned SKU.
Best Regards,
Hitendra & Dotstore Team