Kevin Lewis provides a detailed guide on incorporating subtitles into HTML5 videos using Deepgram's transcription services. He explains the process of generating WebVTT files for subtitles by using Node.js and the Deepgram SDK to transcribe an MP4 video. After setting up a basic HTML video player, subtitles are added via a <track> element within the <video> tag, specifying attributes such as src, label, kind, srclang, and default to ensure proper display and language selection. The guide also notes the flexibility to include multiple subtitle tracks, highlighting differences in browser handling, and invites readers to engage with Deepgram for further questions or feedback.