Installation Problem

Unfortunately, the first attempt to install the theme failed.
The style sheet style.css is missing from the theme.
Theme installation failed.

Screen:
———
Theme installation from file: themeforest-mLcoCECK-enfold-responsive-multipurpose-theme.zip
Unpack the package ..
The theme will be installed ..
The package could not be installed. The style sheet style.css is missing from the theme.
Theme installation failed.
———–

Question:
Is an installation from the internal folder enfold.zip sufficient and complete? Or does the installation have to be done from the parent folder?
What do I do with psd.zip?

Why did the error message come “style sheet style.css is missing” ?
Thank you.

(I am a newbie to the field)