[header] How to do the dead bug exercise [title] Lie flat on your back. [step] Sit down and then engage your abs by pulling them inward towards your back. However, keep in mind that some fitness experts see pulling your abs inward as counterproductive and instead recommend that you brace your abs. 
You can try both options and see which one feels like it is working better. Then, use your abs to gently lower yourself onto your back.