Autofill In Safari

iOS & iPadOS

Hi everyone, I was playing around with my Safari settings on my iPhone earlier and I noticed something I have not paid much attention too before, I cae accross the autofill and played around with using my camera to add my card details , but my question is this. How do I use this feature to fill in the details on a Safari web page and can this be done in Yosemite too? If so how? Many thanks in advance.