You can preview the result of your interactive InDesign content either in the iOS simulator (on OS X only), or in the Twixl Viewer running on an iOS or Android device on your Wifi network.
Preview from the plug-in
When selecting "Preview" for an article or publication from the plug-in, you are presented with a list of devices running the Twixl Viewer on the local Wifi network, as well as a list of simulators (on OS X only). So if you want to preview on a device, open the free "Twixl Viewer" app first, then select "Preview" from the Twixl Publisher plug-in palette (whether for a single article or for a complete publication.
If the device you are looking for does not appear in the list, you can select "Use IP address…" to manually enter the IP address listed in the top right corner of the Twixl Viewer window on your device.
Preview from the macOS (OS X) app
Selecting preview in the macOS (OS X) app, presents a popop sheet similar to the list sheet in InDesign.
In order to test whether there are any network issues, go to your browser and enter the following URL:
http://[IP address of tablet device]:53652/check
You should get a result with the device type and the Twixl Viewer version number like:
ipad-retina|4.2.6 / android10|4.2.6 / phone_m|4.2.6
If a soft- or hardware firewall is active on your network, and you seem to be unable to send a preview to a device, make sure to ask the network administrator to open TCP ports 53652 & 53653.