Question [Q] How do I open this HTC app?

Apparently, I have an app on my phone that I don't know how to open.

As far as I can remember, it opened when I downloaded and opened a PDF. I am using the latest version of Viper. I want to open it, because when you click on the dropbox icon, it intergrates your dropbox account with your phone, and you can see it when you go to Settings>Storage.

Of course this is a moot point if someone can tell me how to achieve that otherwise. Thanks in advance!