How to set up Backup Exec 12 to back up to USB hard drives for windows server 2003R2?

Open backup exec and configure storage.  to use more than 1 usb drive, create a pool and add the usb drives to the pool.

Ok, what are the steps to do that?
Where do I find configure storage?
Where do I pool and add the USB drives to pool?
Do I need to pool all the USB hard drives one after another before trying to back up?

Sorry about that, I mis-read your version I thought it said Backup Exec 2012.
In BE 12 you need to set it up as a removable backup to disk folder for each USB Drive, then in your backup specify under Device and Media : All Devices

I only have access to 12.5 But I think it's pretty much the same.
See Attachments.
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Do I need to format the USB hard drives?

Also can start off with two hard drives and add more later?

If they're formatted as NTFS your good to go.  Yes you can add later.

When setting up back for USB hard it only gives me one option for Media Set "Keep Data Infinitely - Do Not Allow Overwrite.
Is there a way to change that. The drop down menu gives me no options at all.