External Drives and Apple OS

External NTFS drives will be read only on Apple OS, to get write access:

Launch a terminal (Applications > Utilities > Terminal)

Type the following command into the terminal to open the /etc/fstab for editing in the nano text editor:

sudo nano /etc/fstab

Add the following line to nano, replacing “NAME” with the label of your NTFS drive:

LABEL=NAME none ntfs rw,auto,nobrowse

Press Ctrl+O to save the file after you’re done, and then press Ctrl+X to close nano.

From:  http://www.howtogeek.com/236055/how-to-write-to-ntfs-drives-on-a-mac/

Seagate has software that will make their external hard drives read/write