Import variable product issue

Hello,
I have a xml for cloths and relevant product and they have sizes (s, l, xl etc) and these sizes write like <size>S,M,L</size> in XML. so im using str replace function for converting comma (,) sign to line (|) sign.
I want to upload all products to variable product and customers can choose a variations in single product page.
But,
I tried everything but i could not success for that.

Please help me this case, which options should i missing?
Thank you