How Do I Change The Site To Fluid Layout?

I need some help!

Where on earth do I change my site to responsive? I am using 4.1.2 and the KB is outdated and I have nowhere else to turn.

I have tried to find where to adjust this but I just cannot do it.

Any help is appreciated

Design->Layouts, look at the left side and mouse over the Main layout. Click the gear icon and click the Properties link on the dropdown. Then you can choose Fluid for Layout width.