× She informed that she wanted to resign.
√ She informed the manager/her bosses/etc. that she wanted to resign.
We say inform somebody of/that something or inform somebody that …: ‘They informed him that he hadn’t passed the test.’
× She informed that she wanted to resign.
√ She informed the manager/her bosses/etc. that she wanted to resign.
We say inform somebody of/that something or inform somebody that …: ‘They informed him that he hadn’t passed the test.’