I have a problem with installing the theme.
the installation failed. He says he misses the style.CSS.
can someone help me what I need to do. So that I it beautiful forum can use.
I'm sorry but I didn't follow you. wpForo installation is a simple plugin installation documented here:
There is no wpForo theme so I don't understand what are you installing. wpForo plugin comes with built-in theme, you don't need to install any theme. You current WordPress active theme is enough.