This is a little older now but same basic steps. You will need to extract the drvers from Dell and identify what folder specificly contains the driver you are needing to add. Then from the boot disk creator you can navigate to that folder. I would not recomend that you shot gun it and just navigate to every folder one at a time but that won't be as useful as importing just the one folder that you are needed.
https://www.symantec.com/connect/videos/adding-drivers-symantec-boot-disk-creator-tech227489