Where do you want to access your DNS-327L from, a local network or the internet?
If you have not already setup your unit read the manual and format the disks (since you are a professional I would recommend that you use RAID 1 for two reasons, 1) it is more reliable and 2) you will still have access to your files even if one disk dies (we have a client that uses two of these on the drawing office network to store their engineering drawings, one is the live working unit and the second is the backup of the first.
Once you have setup the disks you then need to create a user account with a user and password. This again is in the manual and there is a setup wizard to help you do this.
Get everything up and running on your local network before you even consider trying to access anything from the internet.