I am familiar with speckle but I wondered how that is related to your question.
To download the images from ASF Vertex you have to move the desired products into your cart (the download queue) and then you have the following options:
Download the python script (if you have python installed on your machine) and execute it in order to start the downloading (entering your user credentials is required before it starts). I use this option most of the times.
Download the metalink file and use a browser plugin called DownThemAll (https://addons.mozilla.org/en-US/firefox/addon/downthemall) which downloads the filey you want.
Detailed instructions are given here: https://www.asf.alaska.edu/data-tools/bulk-download/