[mistwang]

I need know where is config file?

You should not change config file directly, use the web admin interface.
server's config file is at lsws/conf/httpd_configure.xml
Example virtual host's config file is at lsws/DEFAULT/conf/vhost.xml

I need change start page, how i can do it ?

Make a copy of lsws/DEFAULT/ directory to something like lsws/myweb/
add a virtual host from the web admin interface, by click "virtual hosts" link on the left, set virtual host root to "$SERVER_ROOT/myweb", for detail information, please read the documentation.

You can copy your html files over to lsws/myweb/html/, or just point document root to the directory of your existing web site.