As we noted when we wrote about the Windows Phone 7.5 version of Play To the operation of the app is very simple:
On opening the app you'll need to configure a connection by choosing a WiFi network and DLNA device to connect to. After a connection is set up, which should just take a few seconds, you can choose to share any video, music, or photo stored on your phone to the configured DLNA device.
For photos and videos you can share from a thumbnail view by double tapping on a photo, or you can swipe through an album (detailed view), with each photo being shared as it comes up on your phone's screen. Videos have a similar quick share option, but the detailed view is more useful as you get an on screen pause control and timer for the video being played.
Nokia Play To aims to make it easier to share content from your device on other screens in your home. You will need a DLNA capable device, but it's a standard that is built into increasing number of TVs and set top boxes.
In real world usage we found that some DLNA devices did not support all three media types. This is due to device incompatibility, or because the device does support the required file formats. Nokia Beta Labs in maintaining a list of devices with such issues here.
Both the Windows Phone 7.5 and Windows Phone 8 versions of the software currently have the same functionality (i.e. sending media, from the phone, to a remote device/renderer), but the development team have indicated that they plan to add the ability for the phone to act as digital media server in a future release. This would allow other DLNA devices (e.g. games consoles like the XBox 360 and PlayStation 3) discover, browse and play content from your device (i.e. no need to manually share from phone), something that was previously supported by Nokia's Symbian devices.