Removing URL/website link in Comments section

In the comments form at the bottom, there is a box for the comment, a box for the commentor’s email, a box for the commentor’s name and a box for their website url. I want to remove the box for the website url. My site is more of a teaching site and I do not want folks coming in just to spam or self promote. I did try two plugins that said they would remove that line, but neither did the trick. I am sure it is an easy fix? but a coder I am not.

How would I remove that link box?

Thank you so much for your help!