You have to "escape" the double quote character, in the same way that you add a newline:
printf("line one\nline two\n");
"\n" is a escape sequence that C recognises as a "special character" which represents a newline, and there are several of them but the most common are:
\n Newline
\t Tab
\\ A literal back slash
\' A literal single quote
\" A literal double quote
So to insert a double quote:
printf("Joe says \"Hello world!\"");
Will print
Joes says "Hello world!"
on the console.