What version are you using? Please post a screenshot of your categories and items page and I can direct you. I have given you the steps but maybe your site is using different terminology - is this a site that you set up?
Weighting groups of grades
It is a class that was constructed by our webmaster a number of years ago and I have been updating the assignments and adding new ones as we change texts.
I tried to download the screen print but the system says no because it is larger than allowed. If it is permissible, I can use my personal email to send it. I do need an email address to do that though.