I want to have notification showed both on my iphone and watch, how can I do this?

You can't. Notifications appear on your Apple Watch or iPhone, but not both. If your iPhone is unlocked, you get notifications on your iPhone instead of your Apple Watch. If your iPhone is locked or asleep, you get notifications on your Apple Watch, unless your Apple Watch is locked. For more info, see:

Notifications on your Apple Watch - Apple Support

If you would like to make this feature request to Apple, use this link:

Feedback - Watch - Apple

I've literally been trying to figure this out for the past 5 hours. My husband and I got new iWatches on prime day yesterday and have been getting them set up today. This one stumped me. I kept texting him and he was getting it on his phone but not his watch. Everything I read, led us to believe we had a wrong setting under notifications. I finally decided to come to Apple Support. Thank you SOOO much. (Yes, we just tested it with his phone off and he finally got the notification on his watch!!!)