How do I find the Activity App on my iPhone? I have just got an Apple Watch, and have adjusted my calorie and stand up goal and received some achievements from my Watch.

When the Activity app is open from my watch, I can open the Activity app via Handoff, but when I search the app from Spotlight, I can't find it. I went through all of my apps in my home screens, I can't find it anywhere. 

How do I open the Activity app on my phone without Handoff?
This morning, I updated to iOS 8.3 and the Activity app now appears on the last page of the home screen.

So I would try to either update to iOS 8.3 or restart the phone if you're having this problem.