The wiki pages listed on the following page might be a starting point.
https://senbox.atlassian.net/wiki/display/SNAP/Processing
You can find also some interesting material in the Tutorials section. In the category for Sentine-1 and also in the external category.
http://step.esa.int/main/doc/tutorials/
Please try again to download. I just tried it and it works. Might have been some hiccup.