No worries, we're here to help.
I'm 99.9% sure it'll be a Gen 1 if it's that old.
Take a look here: Install ClockworkMod Recovery On The Orange San Francisco / ZTE Blade
and use method 2 for installing clockwork, choose your ROM and off you go.
Have a read through and let me know if there's anything that seems confusing before you do anything though. Shout if you get stuck.