VCV means "vowel consonant vowel", which is the format that the lyrics need to be written in.
CV is "consonant vowel".
For example, in romaji it could appear like this: [ka][e][ru][no][u ][ta][ga]
And in hiragana like this: [か][え][る][の][う][た][が]
To convert it to VCV, each note needs to "borrow" the vowel from the previous note.
That would result in this: [- か][a え][e る][u の][o う][u た][a が]
If you need to automatically convert the lyrics for a whole UST all at once, you can use a plugin. Bizz's iroiro plugin includes CV to VCV conversion as well as many other useful features. You can download the latest version here:
https://ux.getuploader.com/bizz_v/download/180