Not all eBay categories have variations, if you would like to create a variable product, please be sure that the Category has a [V] next to it - this means that it supports variable products.
Within Ad-Lister, there are two ways to create variations - you can create variations by using the Wizard or manually
Please bear in mind the following when creating variations:
-Each variation must have a different SKU number
-Custom columns can be added
-Images can be added to each variation (Some platforms require a minimum image size of 500px)
Here we are going to use the Wizard :

Create custom columns for whatever you need for example: color/size
When you are done creating them and updating the needed data you can go to upload the images
You can upload any picture with an image link(URL), from the device you're using or choose one from your Ad-Lister Gallery