Step 1 : Download and install iCloud on your computer.
Step 2 : Run it and sign into your iCloud ID and password.
Step 3 : In its primary window, tick Contacts, Calendars, & Tasks with Outlook.
Step 4 : If you wish to sync email, you will need to create an iCloud email address if you haven’t already. Use the "Create an iCloud email address" link at the top of the window to create an email account.
Click Apply. Wait a moment. When it's completed, Contacts, Calendars and tasks on your Outlook will become accessible in the iCloud.
Step 6 : On your iPhone, tap Settings > iCloud. Sign into your iCloud account. Then, turn on Contacts, and Calendars to sync to your iPhone.
Step 7 : Your iPhone will ask you what you would like to do with existing local contacts, calendars etc. on your iPhone, select Keep on My iPhone in order for the sync to take place. Any new contacts (from your iPhone) with regards to your existing Gmail contacts will be placed in the All Contacts group.
Step 8 : Finally, in order for the sync to begin, go to your iPhone settings, and tap on Fetch New Data. From the newly-opened slide turn Push on.