Your tenancy role decides which parts of Conform you can see. Your workflow roles decide which moves you can make on each board. You need both to work on a board.
Give someone workflow roles
Open Settings → Users & Roles.
Go to the Workflow roles tab.
Tick the roles each person should hold in each workflow. Each tick saves straight away.
Good to know
Workflow roles can be changed at any time; it isn't a workflow change and doesn't need publishing.
You can't change your own workflow roles.
Every grant and removal is recorded in the activity log.
You need permission to assign workflow roles (the owner and administrators by default).
Someone with no workflow role can still see a board but can't move anything: columns show as locked.