Problem publishing tutorial output to my computer

I have just purchased Captivate 2019 and I am busy with the tutorials. The first one is about LUNARSHPERE STUDIOS. I have followed the tutorial to the letter, but hit a “wall” with the publishing. I get an error every time. I don’t know if it is relevant but it appears that “/assets” is automatically added to the title when publishing. Could this be the problem? See the three screensho ts attached. Thanks in advance.