Decreasing at the top of a fair isle mitten, help!!

I am knitting herdsman mittens in fair isle and have been having the hardest time trying to figure out the knitting pattern I am following and I need some help! It says that I need to “continue knitting as set by chart and decreasing one stitch away from the edge every round as described until 20 stitches remain.” I am knitting on 5 needles so I’m not quite sure where the decrease is…I feel a little dumb asking this question but thought that I would come here and as all of you expert knitters on what I should do! Thank you so much!

Welcome to the forum!
Have you placed sts for the thumb? That should help you mark the placement of the decrease lines at the top of the mitten.