You can use the step counting tool in Health that comes with iPhone to count the steps. The specific steps are as follows:

1. Find "health" (with a red heart logo) in the iPhone, which is a built-in function of the iPhone mobile phone system.

2. Fill in personal information (optional). If you don't want to fill in, you can skip it directly or click the "Continue" button below.

3. Successfully entered the "health" function. Click "Start Using" to enter the function home page.

4. Click "Health Data" → "Fitness Record" to view today's walking steps, walking+running distance and other data.