No, very easy to do, purchase a nice 1TB or 2TB Hitachi or Toshiba or Seagate HD at best buy, or amazon.com etc.
$65 1TB
or $100 for 2TB HD either 2.5" or 3.5" HD
you format the HD, then drag and drop files to it.
You should always however have 2 minimum external HD to prevent single choke point failure on an external HD. Because any and all HD can and will fail
when you get your hard drive
o to DISK UTILITY and verify what it says your HD is formatted as under the "ERASE" tab
HFS+ above is the "mac format"
Format (erase) it in "mac osx Extended journaled"
AFTER THIS YOU CAN DRAG AND DROP FILES AS YOU LIKE 😊
Or you can turn your external HD into a Time Machine for data backups
see differences here:
Methodology to protect your data. Backups vs. Archives. Long-term data protection
To show HD on desktop
go into FINDER at top then PREFERENCES then GENERAL tab
then check "hard disks" and "external disks"