How to sync steps between my watch and my iPhone?
Your iPhone and your Watch each track your steps independently. By default you see the steps tracked by your Apple Watch on your watch, and steps tracked by your iPhone on your iPhone. If you want the steps to be combined, you have to enable Apple Health Sync.
How to go in sync
Once you are in sync, you might experience that your steps etc. are not updated immediately. This is because your iPhone is now 100% in sync with Apple Health, and Apple Health updates your activity data only every other minute. The step count on your Apple Watch is always live.
Note that after the sync your step count might increase or decrease a bit, depending on your lead device.