How can I manage rhythm contraceptive method if woman has irregular periods?

You can't. The rhythm method presupposes that there is a "safe" period in which to have intercourse. Ovulation can occur more than once in a given monthly cycle as witnessed by parents of fraternal twins. My definition of the rhythm method is "getting pregnant to the beat.".
You don't. This is not really birth control. In theory, it is a way to avoid the most fertile interval, but doesn't eliminate risk of pregnancy. Women with irregular cycles have conceived during unprotected sex on any day of their cycles, including during menses.