If you have an .ics file ready to go, you can upload it into your document library and link it in your mailing:
- From the Campaigns page, click on the Documents button near the top-right.
- Upload the .ics file.
- Open the mailing where you'd like it added, and click to edit the designated text box.
- Highlight the text you'd like linked -- "click here to add this your calendar," for example -- and click on the link icon in the toolbar, just like you would to add a URL.
- Select the Documents tab at the top, and select the file that you just uploaded. Once you hit Insert, you're done!
Now, just save your mailing, and when it's sent out, anytime someone clicks on the link, they'll be prompted to add the event to their calendar.