iPhone and Microsoft Outlook integration

If the calendar is part of the email account it can be automatically synced by checking the relevant switch in the account settings on the iPhone.

If its stored locally on the computer, you can use iCloud for Windows to sync certain items such as Calendar, notes and other things between Outlook and iCloud, and those can then be synced to the iPhone.

See here: Get help using Outlook with iCloud for Windows - Apple Support

If you are using Outlook as just your email client, then you should be able to set up your email account in the default mail App or any 3rd party mail app of your choice if you have the proper set up information.

You will need to contact your email provider, and get the configuration settings for your email account. Server, ports, settings etc...

This is not really integrating with Outlook as Outlook is just your mail checking app not your actual provider based on what you have said.

See here: Add an email account to your iPhone, iPad, or iPod touch - Apple Support

You would use the "other" option in that case to set up your account.