[mattydr67]

Mate first of all the procedures you can get step by step in tutorials
Ok if you want I can tell you with other words what can read there.
First of all you have to see what kind of tool you've got
A FTDI BL/Bm or RL one
After this you have check the tutorial for your kind of tool
If you cannot figure it out what kind of interface you have then you can share to pics with your both sides of your PCB and I will tell you what tutorial you have to use.
After this you'll need, dumps for the version you want, then you need solder station for smd, then you need to be ablle and have skills in solderind smd components ( maybe you need to unsolder some components from PCB ) and for sure you'll need to solder 4 wires to the Atmega MCU programming pins.
You also need and external AVR programmer, if you have a RL tool maybe you need an professional externall programmer for GAL/ATF ( only you have this on your PCB - but if you do not have my advise is that your tool is very poor quallity and you can throw it to the gargabe and don;t waist you time with reflashing it ).
Then you need the programming softwear that can be used with your AVR programmer tool
Then we can let you know how to do it ( how to manage the settings in the softwear you'll use and let you know the programming procedures with that softwear )
So share that pics and lets see what will be next
Good luck