Welcome to the forums, Steve.
It would be easiest to create a group in your device.
Go to you Address Book > Menu key > New Group.
Name the Group SMS Group (or whatever you want)
Press the Menu Key and select Add Memeber
Select the contact you want in the group
Repeat that step as often as you like until all contacts are in the group.
Then when you send your next SMS out, just send it to SMS Group and the text will go to each contact in that group.
I would recommend reading over these forums and checking out BlackBerry FAQ - BlackBerryFAQ
for more tips on your device.
To get your software version.
Go to Options > About. ... or
Press Alt + Caps + H ... or
Compose a message and type myver