How do you propose a 13 years girl?

No you don't propose to a 13 year old girl. Ask her maybe when she is eighteen. How old are you? If I was the father of this thirteen year old girl, you would be running for your life. Leave her alone!!!!!!!!!!!!!!!!!

Note that there is a minimum age for marriage, 16 years in many countries/states with parental consent, but enquire locally about your local limit and laws.