You tend to have better luck with learning by going to somewhere like Vocaloid Otaku forums, as they have a "help" section as sorts themselves on how to use vocaloids.
To be honest, using a vocaloid is one part learning about Phonetic data, another part learning about a language itself, and the rest down to music. If you've cracked the first two, the rest will ride on the third one, as Vocaloid functions like most music software, its core interface is familiar to anyone who has used a good software DAW.
If your using a non-English vocaloid, and your primarily language is English, you will need to learn how to learn the language the Vocaloid is in. Or at least how to manipulate it to sound sort of like the language its intended (don't expect HQ results though).