how do i tag a utau nico nico upload

i know how to upload to nico nico, i just don't know what taging to use for utaus, and how to tag it right when i upload it (i am talking about that drop down that has all the categories when you first upload it.) and what tags are for utau covers of vocaloid sounds. and how to tag a song that has both a vocaloid and utau in it. and how to tag a song that is a cover of a song that is not sung by or wasn't originally sung by a vocaloid, like anime openings/closings..

The best category for an UTAU video would probably be the music (音楽) category. The tag for general UTAU cover songs is UTAUカバー曲 (UTAU cover song), while for Vocaloid covers, the tag is VOCALOID→UTAUカバー曲 (Vocaloid to UTAU cover song). For a song with both Vocaloid & UTAU in it, you can use UTAU・ボカロコラボ曲 (UTAU & Vocaloid collaboration song), or VOCALOID&UTAUオリジナル曲 (Vocaloid & UTAU original song) if it's an original. Hope that helps!

thank you ^___^