Inventory, categories, characteristics

Hi,
I am excited about evaluating your product, but ran into a snag.

I have products that vary in size and color.

How do I specify the correct category and characteristics so I can track inventory?

For instance, I have a harness (for dogs) that comes in small, medium and large and in colors of red, blue and black.

I created:

Category "Training Products"
Product "Harness"
Characteristics of "Color" and "Size"

I put the corresponding details; red, blue and black in "Color" and small, medium, large in "Size"

But, I can't seem to find a way to change inventory per characteristic, just product.

Please advise.

Thanks.

Thanks for the fast response. Worked like a charm!