Only the owner of an Group can adjust the user rights. To adjust a user's role, go to "Chainweel" on the top right corner of your screen, click on "Groups" and select the Group you want to adjust.
A list of all members of this organization will be displayed. Here you can select the user you want to adjust roles for. When selected, the role of this user can be chosen. Default or Read Only.
With Read Only, he/she will not be able to upload files to this organization.