First, the file uploaded has to be a specific format. This format is MP4 with H.264 video (baseline profile) and AAC audio (low complexity profile, or “LC”).
If the file is a different format, you have two options: encode it on your own (we recommend trying out https://handbrake.fr/ which is a free program) or transcode it on DaCast after uploading. Here is a walkthrough for transcoding.
Second, you have to use the iframe or JS embed code when you have the file embedded on your site. This code is found under PUBLISH SETTINGS.