As per your query, we are giving you some easy steps to add content and for video image change.
Go tp Dashboard >> Aperance >> Customize >> Theme Settings >> About Section >> In which you will get “Section Description” to add content and “Video Image” to change the image >> Publish.
I understand your instructions BUT that section WILL NOT accept Paragraphs. It only will make one block of text. you have the admin login-in already would you please look into this?