Once you have ordered your digis, you should receive an email with the subject:
[Twistoon] "The virtual product that you bought is available for download"
This may be in your spam folder, this contains the links to download your products. 
You can also download your digis from the site, by going into your account on a pc or mac, you can find the link to get to your account at the top right hand side of the screen. 

Once connected to your account, you can choose "order history and details", then, on your current order, click "details" on the right hand side. The text should show in blue.
You can then click on the blue link of each digi to download that digi to your pc. 
If none of this works, please send me a message by using the contact form here: https://twistoon.com/digistore/index.php?controller=contact