I just checked the info about this app via the App Store, and I found now indication that the app provides for viewing WMV files sent as an email attachment. This was copied from the developer's website.
Browse your favourite websites using the app’s fully functional web browser – if the website contains video files, click on the video you want to watch – and if the video file is in wmv format the app will download and play it through the iPhone’s media player - its that simple!
There is no workaround for this. WMV is a Microsoft closed proprietary format. Microsoft formally provided and supported a Windows Media Player app for OS X on a Mac, but they discontinued doing so many moons ago. To view WMV files received as an email attachment on a Mac, or video provided via WMV on a website which isn't very common in my experience, you need to download a 3rd party player called Flip4Mac.
Since Microsoft doesn't support Windows Media Player with OS X on a Mac and hasn't for a very long time, I doubt they will be providing a Windows Media Player app via the app store for an iPhone, iPod Touch, and iPad. Unless Flip4Mac decides to do this, you won't be able to view WMV files sent as an email attachment.