You need to follow below tutorials for setup size attribute as swatches.
Hi Mr. Rakesh,
Thanks for your reply, i had follow the link instruction given but still not work. Please advise.
Hi @hea hooi_ngoi,
Take a look to the user guide: https://docs.magento.com/m1/ce/user_guide/catalog/product-configurable-swatch.html
There you'll see how to use and configure the configurable swatches and, I guess, is what you're looking for.