Hi

I have yesterday, started at to work at a mental-health/anti-drug organisation here in Denmark.
We(I) work with high levels of privacy, thats why we use tails, in our online work.
Though the tails-pro(is on holiday for another week, and costly and not a good thing, to call him).
I got handed out from new work, and external harddrive, I can surely figure out how to mount it(in tails), but we(company) rely on, sending supportive files from harddrive to customers.

But gets this messages when I want to attach file from ex. harddrive:
"Could not read contents of Ekstra"(harddrive is called "Ekstra")
Error opening directory 'media/amnesia/Ekstra':
Permission denied.

How do I give file/folder access permission, for other programs on tails.

Sounds like a permissions problem, do you have root access or sudo powers(?), if you do you can mount the drive & get access to the files; if not you'll need someone who has.