# [Tex/LaTex] Document class not available

document-classesinstallinglyx

I'm new to LyX, and using LyX 2.0 for Windows. When I select a template from "File"->"New from template" it shows a alert with title

"document class not available"

containing the text like

selected document class

book(KOMA-Script)

require an unavailable external file and asks for

scrbook.cls

Where can I get the scrbook.cls and how to install it?

Besides TeX/LaTeX, you need to install the KOMA-Script bundle, scrbook belongs to it, as all classes and packages with a name starting with scr.
• If you use MiKTeX, start the MiKTeX package manager (mpm) and install the package koma-script, the link points to the package description on the MiKTeX homepage.
• If you use TeX Live, start the TeX Live Manager (tlmgr) and install the package koma-script. It can also be done on the command prompt: tlmgr install koma-script.