Stocks by attributes

[wheretostartwebsites]

I am working on a site and I am working with the classic template.
what I need to do is:
I have 6 nappies
4 x medium and 2 x small

I have made attributes for the medium and small
what I need to know is how do I add and control the qty,s available for each size.

At the moment I just have the available sizes but nothing for the qtys available I have been reading and reading and just can not find what I need to be able to do this.

This is the site:
http://clothiebumz.com.au/

the owner wants to launch on sunday so i really need to get this finalised..

Thanks in advance for any help you can give me..

I think i have found the add on to be able to do what I need to do.
attributes_separate_stock_v0-1. is this what i need..

would someone be willing to install it for me as i am not familiar with SQL..
I am happy to pay someone to do it for me so i can get it right the first time.
TIA