Timestamps can be imported automatically from some websites using the browser extensions. For example both automatic and manually entered transcripts/captions from Youtube preserve timestamps when imported. You will have to see whether timestamps exist in the original transcript.
You can also import txt or pdf files with timestamps in them and match them up with an audio file when creating a lesson. You may have a timestamped transcript file or you may have generated a timestamped transcription from a podcast or audio file from an automatic transcription site like Happy Scribe.
Import the text file using our Import E-book feature which allows importing of files. Just hover on the Plus "+" button in the top right corner of the website to find this option. Once imported, upload the audio file and then Save to match up audio with text.