|Sorry to hear that. It may not be too late though. Since it's a non-profit organisation, you might be able to find someone who's willing to donate some time. I have done so in the past and helped setup an office, and it's network, servers, and domain for a non-profit organisation.|
I've never used CP Express myself and have done all my work on Cisco products from the CLI.
I can tell you, you'll need to configure an internal IP address on the internal interface. This interface will be your 'default gateway' address for all internal clients requiring external access.
On the external interface of your router, you will configure your TCP/IP settings as given to you by your provider. This will be your external, public address with all associated settings (DG, SM, etc).
Finally, you will have to ensure you have a route set from the internal interface to the external for traffic to get out, and back in. I can't help you much with this. I have a lot of experience configuring Cisco switches, but very little with Cisco routers. We use OpenBSD based routers where I work, ergo my lack in that specific area. I suspect I could figure it out fairly quickly though, but I'd need to be sitting at the console to do it.
I would also highly recommend you put a firewall between the external interface of your router and the external connect (ie: Internet >> Firewall >> Router >> LAN)
As to the exact commands, I can't tell you offhand. If you can't find help, I recommend doing some searches on Cisco's website for your model router and it's associated CLI. You can also google for setup information since you're looking for exact commands. Don't forget, there will likely be some Cisco forums out there where you could ask for help too...again, explain your situation (ie: non-profit org)
I still recommend you make some calls to local consultants and computer businesses. Explain your situation and need for someone with experience with Cisco products to help you. For a person who knows what they're doing, you're looking at less than an hour of their time to configure the router.....maybe even less than 30 minutes.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.