You will need to place the .ai files in InDesign. Start by opening them In Illustrator. Once you have made the edits, you can save a copy and use File > Place to add the edited file into your InDesign layout.
Awesome! Thank you for the quick reply :-)
What if you don't have Illustrator? Is there any work around or is Illustrator a must?
You will need Illustrator to edit the files with a .ai extension.
Do you have a CC subscription? It will come with the full Creative Cloud subscription. InDesign is a layout program where you combine text, photos and illustrations into an attractive layout. You will need Photoshop (or equivalent) to edit the photos, and Illustrator to edit the vector illustrations. I don't know of any other programs that you can use to edit the .ai files though, besides Illustrator.