Here is something I use to learn the DL (with a kb for the moment), and maybe can help you also:
1. Put the weight on something higher and work separately on hips and hams mobility and flexibility (over time the ROM, form and technique improves)
2. Elevate your toes and the balls of your feet on equal height objects. I use 2 books, but since you have access to a barbell, some plates are excellent. This prevents the knees from slipping forward and teaches you to hinge through the hips and not to lift with your lower back or your knees.
Also, Ben Pollack, a star in powerlifting, has several youtube videos in which he explains the set-up and not only: , .
Hope this helps.