Go to Products, click List All Products, select all of the products in the resulting list, click the PowerEdit button to the right of the list. On the PowerEdit menu select the Quantity On Hand option and/or the Low Stock Threshold and/or the Out Of Stock Limit options, depending on the aspect of the Inventory Tracking you want to modify for the products (these options are all in the 'Information' column). Leave the radio button at the 'Individual' setting (unless you want to set the inventory numbers to the same thing for every product) and then click Proceed. Then you should see a screen to edit the inventory settings for each product. See documentation at:
http://www.shopsite.com/help/8.1/en-US/ ... ducts.html
Note you can also update inventory numbers via the upload feature if you would rather do the data entry offline then just modify the existing ShopSite products by uploading the data. See documentation at:
http://www.shopsite.com/help/8.1/en-US/ ... pload.html
-Loren