A few tips that may hopefully be useful:
For your purpose, click on Disk\Partition, c: will be selected by default (shows in orange, if you have more partitions click on them to add them to the cloning.
Then look at 'Destination'. If your external drive is not listed click 'Click here to modify' to navigate to your drive. Click 'Proceed'.
You need the destination disk to be of similar or larger size vs the source disk. With larger size, the leftover space will be unallocated, can be fixed anytime later with a partition program.
No need to boot from cd or anything. btw, the resulting copy\clone also gives individual access to all files when opened in explorer.
Agree, the interface could have been better\different, but what's more important is getting reliable backups and restores. Go ahead, it'll work out fine, it just needs a little familiarity. Easeus has worked very well here. To the point of feeling guilty with my regular use of the free edition
, time to send them some $ I guess.