When you first open the app you will be prompted 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 or photo stored on your phone to the configured DLNA device. You can change the device you are sharing content to, by tapping the connection entry on the app's opening page and choosing from the available devices.
When sharing media you choose from pictures, music and videos. Content from each of these types that stored on your device is automatically compiled into easy to navigate lists.
For photos you can share from a thumbnail view by double tapping on a photo, or you single tap on a photo, which loads a detailed view page and then swipe through an album, 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.
For music you get a pivot view (artists, albums, songs, playlists, genres) from where you can tap a play button to share all the songs from a given artist, album, playlist, or genre. Alternatively you can tap the artist, album, playlist, genre name to browse a list of tracks/albums and select a specific track/album to play. When playing music you get next/fast forward, previous/rewind and play/pause controls.
Nokia Play To is all about making it easier to share content from your device on to other screens (and into speakers) in your home. While you do need a DLNA capable device, the chances are good there's at least one of these already, even if you don't realise it yet. As such it's a rather splendid extra for your Lumia phone.
Play To can be downloaded from the Nokia Collection in the Windows Phone Marketplace for free, or by scanning the QR code on this page, or via the AAWP app. It is available in all markets. You may need to upgrade your phone's software for the app to function correctly.
Play To was previously available in beta. The release version fixes a number of bugs, includes a number of small user interface improvements and has added the ability to stream music. During the beta period the Play To development team noted that they hoped to add the functionality that will allow a Lumia handset to act as a DLNA Media Server (DMS) in a future release. This would allow other DLNA devices to discover, browse and play content from your device (i.e. no need to manually share from phone).
If you're looking for DLNA software for your non-Nokia Windows Phone device you may already be covered by your device manufacturer. Samsung has All Share, HTC has Connected Media, LG has Smart Share and there's also the third party apps One Player, AV Remote and Yxplayer.