Using Time Capsule as external hard drive

If I'm understanding correctly, I open finder, open Shared>AirPort>Data–and then drag and drop all the files currently on the external hard drive onto this window? Is this correct? Will it COPY, and be accessibe, and not cause problems?

Yes, you understand this correctly. File can be copied/moved to or from the TIme Capsule's internal hard disk drive in this manner.

Another option is to connect the existing external hard disk drive to the USB port on the Time Capsule and continue to use it as you have. In addition you can then use the Time Capsule's internal hard drive for Time Machine backups.

Will there be a problem running Time Machine in the back ground while using the Time Capsule's internal hard drive manually?

No.

Thus far, instead of using Time Machine in an automated mode, I've turned it on when I want to make a new back-up. Will it be necessary to run Time Machine in manual mode only or can I use its automated feature?

Or–I may be seeing the light–will running the two in tandem allow me to save each new back-up on both devices simultaneously, keeping both drives up to date?

I would suggest that you consider changing your backup strategy. Time Machine was designed to be an automatic "run and forget" operation that performs incremental backups of your Mac's internal hard drive. It will also backup an external hard drive attached directly to your Mac. Running it manually is not very effecient and you stand the chance of not getting a very recent (they run once an hour) backup when you need it.

For Time Machine I would suggest that you continue to use your external hard drive as is and dedicate your new Time Capsule for Time Machine backups. If you still need more external storage, you can always add additional external USB hard drives to the USB port on the Time Capsule.

Even better you will also want to include a second "full-clone" method to your backup strategy. This method will make a full copy of your Mac's internal disk drive that is bootable. Why do this? In case your Mac has a fatal hard disk crash, you can use the clone backup to boot your Mac back up and continue to use it within seconds. Without the clone backup, you would first need to install a new drive, then load a fresh copy of OS X, and then, perform a restore from Time Machine. This can take a while.

To perform these clone backups, I would recommend that you get another external USB hard drive with a capacity at least twice that of your current internal drive. I use Western Digital My Passport drives for this purpose, but any similar drive should do. To create the clone backup I would suggest using either SuperDuper! or Carbon Copy Cloner.

I would suggest that you create a new clone backup at least once a month or more often if your data is critical to you. Just connect a dedicated clone drive to any available USB port on your Mac and run the clone software to make the clone backup.

Can I use my Iomego external drive for these clones? It has plenty of space open still–1.35 TB.

You could use this drive; however, during the cloning process the entire drive is first reformatted and is used for the clone. This is why you want to use a drive that is slightly larger than the internal drive so that you don't waste the extra storage space ... and why I would recommend that you get a second drive to dedicate to this purpose.

And if we delete any file that is on the external drive for example an app or a file, how can be recover it? it is an network drive so its not visible in any recovering program

We have already told you in your other post that the file cannot be recovered unless you power off the drive immediately after the file is deleted, pull the drive from the Time Capsule and place it in a caddy or enclosure and use file restoration software to try to retrieve the drive.

If you did not immediately power off the Time Capsule after you deleted the file, the file will be overwritten within minutes, and cannot be recovered.

If the file was important to you, surely you had a backup of this file that you can use.

Please do not ask the same question on multiple threads.