Connect your Pebble to its charger
Connect your Pebble to a plugged in USB charging cable. You really wouldn’t want it to lose power in the middle of a firmware update! Once the watch is powered on, press the left button to dismiss the charging screen.
Install the app from the App Store
On your iPhone, download the Pebble app from the App Store:
Open the Pebble app
If prompted, allow the Pebble app to turn on Bluetooth.
Skip the sign in page
The old sign in page (now blank) will be shown.
Press SKIP in the top left.
Choose dictation language
Choose your dictation language.
To use dictation you will need a Rebble subscription.
Choose the type of Pebble you have
iOS then opens the accessory pairing screen. Wait a moment, then select your Pebble.
Wait for any updates
If required, your watch will now update. Wait for this to complete, then go to the next step.
Select the Pebble language
Choose your language.
Allow LE pairing
Allow the Pebble app to pair with your watch in Low Energy (LE) mode.
Enable push notifications
Allow notifications.
Allow location access
Press ‘Allow Once’. You’ll need to change this to ‘Always’ later for certain Pebble functionality to work, such as local weather.
Setup calendars and Pebble Health
Run through the Calendar and Pebble Health screens. Enabling these is optional, but recommended.
Finish configuring your Pebble
Once you get to this screen, you’ve finished part 1 - connecting your Pebble.
All that’s left to do now is set the location permission and connect it to Rebble Web Services.
Allow location
Open your iPhone’s settings and look for “Privacy.” Then, open the “Location Services” section.
A list of your apps should load. Find the Pebble app here.
Set the location permission to ‘Always’. This is required for things like watchface weather.
Open auth.rebble.io
On the phone, open a decent browser (like Chrome or Firefox), and go to auth.rebble.io.
You should be greeted with a number of ways to sign in.
Choose one and sign in. Remember your sign in credentials!
You will return to the Rebble website, and be greeted with You’re all set!
Press ‘Switch to Rebble’
Read the page, then tap the Switch to Rebble button. If you get a prompt, accept it.
The Pebble iOS app will open. If you get the ‘Configuration change’ prompt, press ‘Change’.
Wait at least fifteen seconds before proceeding to the next step.
Tap the exclamation mark
After waiting, tap the yellow exclamation mark in the top left of the screen 
You’ll see this menu.
Press ‘Log in.’
You’re done
You should now see this screen:
.
Press ‘IT’S REBBLE TIME’.
You’re done!
You’re done! Tap the big “+” in the lower right corner and find and install watchfaces you like from the Rebble appstore.
If you want to use dictation, get weather pins in your Timeline, and have a faster Timeline sync period, check out a Rebble subscription