Step 1: Sign into Outlook webmail via https://outlook.com.
Step 2: Click sign-in button on the top-right corner and sign in with your username and password.
Step 3: Click on the Settings gear icon on the top-right and scroll down and click view all Outlook settings.
Step 4: Switch to Calendar tab and navigate to Shared Calendars.
Step 5: Choose the Calendar from Publish a Calendar section and click Publish.
Step 6: Copy the link respective to ICS and use it on your website.