How to create a simulation using Captivate 8 ?

That is what Captivate was originally designed for: software simulations. Use that kind of New project, Record Software simulation (is also on the Welcome screen, New) and be sure to check Training (better, check also Assessment and Demo). What will happen can be checked in Preferences, Recording, Modes (settings for the 3 recording modes). The text that will be added (you can choose the language before capture) can be edited in a file with extension rdl. Each slide that will be captured, you'll hear a camera click. Both text, click boxes and TEB's will be added automatically but it never hurts to insert an extra slide during capture using the Print Screen button (see Keys for the shortcuts in Preferences). After ending capture with the keyboard key End, you'll have three files (if you checked the 3 modes) that you can edit easily: text will be in a normal text caption or in a shape if you checked that preference and allows normal editing. Same for TEB's, click boxes, highlight boxes. I tend to change the default highlight box before capture using a bright color and more width for the border than the very fine light blue one that is default in most themes.