As a workspace team member, you can add available custom fields to your canvas. This requires them to exist in your workspace settings (accessible only by workspace admins) at the time.
For more information about your workspace settings, see: Creating and Managing Custom Fields
To add available custom fields to your canvas, click Insert - Custom Field:
Now select the custom field(s) you want to add to your canvas and click Add Fields:
As mentioned on screen, custom fields can be assigned to a Ruum once. However, multiple references to that custom field can be added to the same canvas. Whenever data is inputted into one reference it will then be automatically copied or change in the other references.