For a user to be able to edit a version, he needs to become the editor of the version first. For this it is required to perform a workflow step:
In your personal preferences you can specify that CMS Fiona should perform workflow steps without asking the user for confirmation. This setting does not apply to the workflow step take because it should be considered that the current editor of a file's draft version is not notified when someone takes the version and thus might lose his work.
If you have activated the confirmation of workflow steps in your personal preferences, the step can additionally be commented. This text then appears in the task list of the user or user group responsible for the next step.