I cannot choose different layouts

Hi David.
Im assuming your video is vertical.  The pre-set layouts are made by adding bars above and below the video.  With vertical videos there isn't any room so if you want to add a bar just add a headline and then add a color to the back of your headline.  (note it's transparent by default so make sure you adjust the transparency slider.)

if you need further help with this let me know and I'll do it for you.
– Craig