As soon as you have made a purchase with your card, you will receive a notification on your phone. The notification takes you to the transaction and you can immediately take a picture or upload documentation for your purchase.
You can also choose to upload the receipt at a later time by using the app:
Take a picture of your physical receipt and upload in the app.
Log into the app, go to "my transactions" and select the current transaction you want to add your receipt to. Click on the transaction, then on "receipt" and select the image of your receipt.
Share a pdf file of your receipt into the app.
Open the pdf on the phone and press "share". Share to the Mynt app and select the transaction that the purchase and receipt relate to.
In the web environment:
Upload a pdf file or image of your receipt.
Go to "my transactions" and select the current transaction you want to add your receipt to. Click on the transaction and then "choose file" in the box that appears on the right.