Woocommerce setting sizes & quantities

Hi Just checking out the woocommerce plugin for use in an online shoe store.
I’m trying to set up individual quantities for multiple shoe sizes for a single product but it doesn’t appear to be straight forward.
I’m using different types of sizes as Attributes for example
UK Mens Sizes
US Mens Sizes etc
with the actual sizes listed as terms for each Attribute.
Now I’m trying to apply quantities to each size within the product page but I can’t find where to enter them.
Has anyone got any experience with this plugin. I’ve checked the docs but can’t find a solution.
Thanks