Step 1. click on my ebay, then click on all selling. All your listings will be visible.

Step 2. go down the list and tick each box next the like minded items that will go into the one category. (if you miss some it doesn't matter)

Step 3. Above all the ticks their is an edit button, click on that. It will bring up a new window, wait for the listings to appear.

Step 4. Click on all the tick boxes again. (tip if you click on the very first box it will tick all of them for you)

Step 5. click on the Edit Fields button drop down menu select categories now you will see there are 2 boxes along side store categories they will both display no change.

Step 6. In the first box click the drop down and select Change to a new box will pop up with all your categories just click on the one you want.

Step 7. Press save and close wait for it to do it's thing then click submit changes and I think it will get you to confirm again.

Repeat the whole process untill all your listings are in their categories.