Need help with Vibrato.
 

My instrument is a Viola. Well, I need help with Vibrato. I'm playing at my aunts funeral in 1 week or so, and i'm not that good of a Vibrato(er). I'm great with my Viola though. Any tips or helpful information will be good.

You don't have to use Vibrato - it's a form of expression of feeling, also that sound should never happen randomly.
How to Do Vibrato on a Violin: 13 Steps (with Pictures) - wikiHow
Maybe that wiki article helps you, but of course, you'll have to practice a while.
Just don't get exasperated with it, if you play the piece well without Vibrato there won't miss much.