How to use Borderlands 2 Save Editor?

Hey guys I was messing around with the save editor last night and I can't seem to get it working.. Is there any thing that I am doing wrong? Like little things that I am missing.

I was trying to mod my guns, skill points, money etc.

 

you need to open your save up on on horizion 360 ect and go to contents extract the savegame file then open it up to mod it when done save it and replace ur modded savegame wif the old one

 

if you have downloaded blitz save editor then you should also have his TUT with it

 

I also seem to be having a problem with this. I extracted the savegame.sav file, edited it in the Save Editor, saved it, then tried to replace that file with the new one. I keep getting a "object reference not set to an instance of an object" message.