I have discovered how to do it.
use the drawing at the bottom of this pagehttp://arduino.cc/en/Guide/ArduinoMini
mine is an UNO not an NG but wire it the same.
The UNO has a rst next to the 3.3v socket but it works with the reset on the mini set to either pin 1 or the reset socket of the UNO.
go to tools/board on the loader and tick arduino pro or pro mini.
go to tools/processor and check 'atmega328 (5v 16MHz') is checked.
Make sure you have good connections to all the five holes of the mini (I used a bread board and soldered the supplied strips to just the required holes as I intend using the boards without the rows of pins). I think I might have been getting the error message seen before due to bad connections.
The boards I bought already had a programme in them flashing at 1/2 second intervals which showed on the onboard led and pin 13 when I touched it with an LED.
I am using 1.5.4 version of the software.
Just for clarity ......it is rx on the UNO to rx on the mini and tx on the UNO to tx on the mini.
Thanks to all who gave me a sensible reply.