Access Apps From the Dock
You can quickly access your favorite or most-used apps through the dock. Just press the side button and scroll through the list until you find the app you want. Apps can be added to the dock. If you want to remove one, swipe it to the left and tap the X.
To better manage your docked apps from your iPhone, open the Watch app. At the My Watch section, tap the entry for Dock, then tap the Edit link. You can then remove an app from the dock by tapping the minus sign, or add an app by tapping the plus sign.