如何为UIScrollview中的一个按钮留出底部的边距?

I have some UIViews (labels,textviews,buttons) inside a UIScrollview. I used IB to design UI. I want to put a button margin bottom 20px to uiscollview. In android it's easy for me to margin bottom/top/left/right for a view to other. But how can i do that in iOS? I have to code for this or just adjust some info in IB?Im quite new to iOS, please help me. Thank a lot!I have some UIViews (labels,textviews,buttons)