There are two main options for working with Add to Calendar files in Eloqua: 

1. Download a File:

If you already have an .ics created via a calendar system, you can either hyperlink to where it is hosted (i.e. on a Calendar system), or you could download the .ics file and upload/store it in Eloqua file storage. Here is a KB on: Uploading Documents to File Storage to Create Links.

2. Use "Add to Calendar App" within Eloqua:

We do have a new .ics "creator" app installed now in Eloqua, called the "Marketing Decisions Add to Calendar App."  With this app you can enter your calendar invitation details and the app will create an .ics file hosted on the app's website. You would then use this link as a hyperlink from within your email asset. The recipient can click the link which would download the .ics file.

If you're interested in this option, you'll want to follow the instructions exactly. 

MD Add to Calendar Instructions for UW–Madison

We cannot stress enough how exacting and diligent you will need to be when following the steps of the instructions as you input your event details. 

Please keep in mind both of these options involve your contacts/recipients downloading a file and saving it to their own calendar system. Any updates you make to the original calendar invitation will not be reflected in the .ics files that are downloaded, similar to a .pdf document remaining static after the end user accesses it. If you need some flexibility to adjust the event, you will want to use Outlook or another method to create your calendar event.