You can ignore the margins & let Instagram crop your image. It's actually easier to use the centre of the image. Make sure you don't place any critical information in the margins.
2
Name & save your deck to a folder on Dropbox
You’ll need a dropbox account installed on your phone & your desktop.
3
Save As / Export To (Images/jpg).
You can save decks as HTML, PDF & Images. Images make it super easy to share & reuse your content.
4
View Images via Dropbox on your Phone (search for folder)
It may take a minute for the images to sync to dropbox on your phone.
On iPhone you need to save the image to your phone
5
Open Instagram, choose photo & publish as normal.
Choose existing images (see your most recent photos). NO need for a filter.
It’s rarely best to post multiple images at once on Instagram