I am the only one working in my office. What can the VoicePro do to help me?

The best idea is to just mention to press zero for assistance in your company greeting. That will ring to extension 10 (the operator extension) by default.

You can also assign up to 99 mailboxes to take messages for various tasks or company departments that you will handle by calling back later.

How can I make all the extensions in a group ring at the same time?

You can assign any menu option to ring one or more extensions. Say, for example, that you prompt your caller with "for customer support press 1" and you have three people who can handle customer support. Let's say they are at extensions 12, 13 and 15.

You can use function 44 to assign menu number "1" to ring to 12, 13 and 15 simultaneously. As soon as any of those extensions is answered, the others stop ringing.

If no one answers then the caller will hear the greeting you have in the mailbox of the first extension in that list, extension 12 in this example. Then they can leave a message in that mailbox.