Find the use you wish to remove in the collaborators table and then use the select options to modify their permissions. Permissions have three tiers -- 'update' (view and edit), 'read' (view only), and 'none' -- and include the following categories:
Project: Anything related to project metadata (description, billing contact, etc.) and collaborator/citation management.
Tags: tag deployment metadata.
Stations: anything relating to station management including station deployment and landowner information.