I think an attribute is a spec of a product, like size and color, as you mentioned. When you add a new product there should be options to add those attributes.
Edit – Ok, make a new product first, then go to Product Attributes on the left. In the top tables you can add new custom attributes. In the bottom table you need to select the product from the dropdown at the very bottom then specify the attribute and detail (blue, red, large, small, etc). Looks like you have to do this for each attribute for each product.
I think an attribute is a spec of a product, like size and color, as you mentioned. When you add a new product there should be options to add those attributes.
Edit – Ok, make a new product first, then go to Product Attributes on the left. In the top tables you can add new custom attributes. In the bottom table you need to select the product from the dropdown at the very bottom then specify the attribute and detail (blue, red, large, small, etc). Looks like you have to do this for each attribute for each product.