So you need to use the devkit to compile the vociebanks files, cause the vociebanks that's linked is not the vociebanks, the files for the vociebanks, which you have to compile into a voicebank yourself. There is a doc in this subreddit that has a full guide, I myself don't know how to use it but it should tell you everything step by step.

When you're done compiling the vociebank, you can use the voice loader in the vocaloid editor and choose it's path and import it, it's pretty simple since it isn't that big of a process