I'm on with making some (not the dev, just a fan), but there is a question mark next to most bits that explain what they are.
You're best off changing the simple/expert slider at the top to on - that will get you expert mode. Sounds scary, but I find it much easier as it gives you a menu list that lets you add in and create stuff more easily.
There is a drop-down menu near the slider in expert mode which will give you access to the individual bits: actors (characters); user interface (UI/UX), where you can change what is there already, or add your own custom designs; and locations, though there's plenty more.
To build your game easily, the simpler way is: add your characters, with their names and appearance; add your locations; THEN start adding your dialogue. To have branching paths, you can add those as options in the same screen as you do the dialogue.
When you complete your dialogue you'll be almost finished! Check through everything, add in sfx and lighting, edit what you need to, then do an exported file for testing. If your test is okay, then you can start uploading it to different services. Make sure the file and test is fine on PC, then you should be alright to export to mobile.
Hope that helps!