If you have received a receipt in your email, you can easily forward it to the service.
You can find the email address for this in the menu on the left under Forward email Receipts, as shown in the image below.

 Just make sure that you send your receipt from an e-mail address that is linked to your account. You can add more e-mail addresses in the Settings view.

When the receipt has been processed an expense will automatically be created for you to add to an expense report. 
 

For more information on how to submit your expenses: Click here