If you are a university student, your civil engineering department’s digital library likely hosts these manuals. Reputable engineering portals and forums (like the official CSI community forums) often have stickied threads with links to the official documentation.
One of the biggest challenges with this keyword is finding a safe, legitimate source. A quick Google search for can sometimes lead to file-sharing sites riddled with malware or outdated documents. Here are the recommended ways to access the documentation: etabs user manual pdf