After compiling the LaTeX rightly, I try to view the .pdf file. But it said that

.pdf file not found.

I think maybe I need to correct some settings?

I am a beginner

Thank you very much!

\documentclass{article}
\begin{document}
Hello, world!
\end{document}

• Welcome to tex.SE Would you mind posting a Minimal Working Example that will illustrate your problem? Thank's! – Thanos Sep 5 '14 at 15:21
• Your question is not well posted. You can have a look at our starter guide to familiarize yourself further with our format. – user31729 Sep 5 '14 at 15:41

As you can see on your screeshot you are using the LaTeX engine. Instead of a pdf, this engine provides a dvi-file.
You should use PDFLaTeX instead of LaTeX (choose from the dropdown list), which should output a proper pdf. See screenshot below: