Go to the Health app on your iPhone to set it up. You have to be over the age of 22 to use this feature. Once it’s set up on the iPhone, open the new ECG app on your Apple Watch. Rest your hand on a table and put your finger on the Digital Crown and wait for thirty seconds. Try not to move during that time. After the set time, your ECG report will be ready. You’ll be notified if Apple Watch suspected something wrong with your heart rate or if you show signs of atrial fibrillation.