Ask How do you create a responsive join page design for a membership site?

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I'm building a membership site and need help with the join page. I want it to look great on all devices. I've heard about responsive design, but I'm not sure how to apply it. I'm using a simple layout now, but it doesn't adapt well to smaller screens. I've tried using templates, but they don't fit my needs. I need a design that works everywhere. How do I create a responsive join page design for my membership site?