i can't drag and drop to my seagate external drive

How is the drive formatted. If you don't know click it and type Command + I and look for something that looks similar to:

Then let us know what the format is set as. Is this Seagate supposed to be a backup hard drive and are you backing up?

The device is formatted for Windows, as NTFS. The format is readable, but not natively writable on a Mac. To write to the device, you must either reformat it (erasing all the contents) or install third-party software to enable write access to NTFS.

boobookitten wrote:

does this mean its not set up for Mac at all?

That is correct, OS X cannot write to NTFS, it can read files from the drive. If the drive is only going be used with your Mac then it needs to be re-formatted to:

Mac OS Extended (Journaled) (GUID) partition. My guess is you don't know how. To format it and learn about Disk Utility please click

http://www.macworld.com/article/2987201/operating-systems/hands-on-with-disk-uti lity-in-el-capitan-tool-for-storage-devi…

Hello

I had the same issue

I read the article suggested by your kind helper :-)

I also found this one which was simpler, step by step, with screenshots

http://www.macworld.com/article/2990837/storage/how-to-format-a-startup-drive-in -el-capitan.html

then plugging it in, it won't show up

following this article

http://www.macworld.co.uk/how-to/mac/how-fix-missing-hard-drive-3613422/

but no success yet!!

I have existing apple files I used as a total back up on my 4tb Seagate, but it still won't let me transfer any files now what-so-ever ? And reformatting it totally won't be a problem, I just wonder if there is a way not to ?