To change the pronunciation for any word, select it and click Tools >> Pronunciation. Enter the word you want to correct the pronunciation for in the Word text field. Enter the way you want the word to be pronounced in the Pronunciation text field. Click the Test button to hear the pronunciation and click Apply if it is correct.

Use this method in Text Speaker to correct the pronunciation for each incorrectly pronounced word in your document.

To learn more about Adjusting Pronunciation see this link:
https://deskshare.com/help/ts/AdjustingPronunciation.aspx