You can d/l 1.4 and updates Hammer3.5 FGD here
http://spirit.valve-erc.com/index.phpOr Version 1.2 from further down the page (also has a 3.5 FGD d/l link in the next post up).
The Very latest version..which is BETA (although reported to be more stable than the full 1.4 release and requires to be updated via another version is here.
http://www.whiteplasma.com/sohl/wiki/index.php/Development_sohl_1.5Tutorials....none of any use I could find.
If you need to work out how to use it...either search the forums for answers (community is not very active...average reply time to a post 2-3 days) Also look at the entity list under features on the main page, this will give you an idea what is avaliable and what parameters you can control. The rest is really down to you...there is not much support and the website links to any further info on using SOHL are mostly down.
Good luck...its a great little MOD to map with...but you have to search and find stuff if you want to use it properly.