I have a custom list and a workflow with an initiation form which obtains information from the user, but also I need to display the fields from the record that the workflow was initiated and allow the user to edit those field and write back to the sharepoint
Sorry, initiation form is used for workflow configure purpose. It means before your workflow code started, initiation form has already finished its authoring process, your code cannot touch it and modify something in it. So
you can't display the fields from the record.
But I think you can set your workflow auto started when custom list item created/modified, then you can fulfill your requirements by association form or task form