lens change

Hello! I have gotten cheap rootbeer Four S - user condition, but I dont mind as I want to wear them. The thing is, the glasses are fitted with prescription lenses, which I will need to replace before wearing. The lefthand lens has an O etching, so I'm assuming the installment was made by Oakley...

Here's my first question and it's a simple one. The Oakley Crosslink frames feature easy user replaceable lenses. In fact there's videos all over YouTube showing you how to do this with either the Crosslink or other Oakley frames. My question is what would Oakley expect to be the normal cycle...