Upon successfully completing a purchase, an email confirmation will automatically be sent to your email address. Your tickets will be found in a PDF file attached to this email address. To download them, simply click on the attachment and (providing you have an up-to-date PDF reading software) your tickets will be displayed.
You can also log in to your Billetto account (On the Web or Mobile App) and click on the 'My tickets' in the top right hand corner of the screen
Here you will see all of the tickets you have purchased. Clicking download will (unsurprisingly) begin the download of your tickets.
If you still cannot download your tickets, then check this page here
Finally feel free to contact Billetto Support, You can do so by clicking here.