hi, I activated User album, because I want every user who registers has its own album. But I want this album to be inserted into a main album called USERS. is it possible?

No, please see the info box below the section here why : http://www.zenphoto.org/news/an-overview-of-zenphoto-users#zenphoto-users

THANKS
then there is a chance to highlight the home only a few albums?

Do you mean only to show specific albums? See the article I linked how to hide albums.