Hello,
In Captivate 2019, you will create a new video demonstration project. Next, you will import your video on to the slide. When the video is imported, the time-line of the slide will extend to the length of the video. I identify the point in the video at which you want to have the topic name appear and click on the time. In doing so, the slide timer will move to the clicked position. I would then click the Textbox button. A text box will appear on the screen. You can change the text to what is needed. You can also adjust the time the text box is displayed by adjusting the text box on the time line. The loner the text box is on the time line, the longer the text will display on the screen.
Good Luck!
Peter