carb my son turned a screw on carbretta dont start

[truebrummie]

my son tuned a screw on the carbretta but it wont start what do i do to fix it help pllllzz???????????

 

[slick 50]

i think it would only be the idle screw ??
as most carbs have the air mixture screw underneath ,
Just turn it in a bit at a time until it starts