Ba Zi basic still not understand

Hi,

I am very much interesting in bazi i read few books and also search on video but still i can't understand basic for example what is Heaven Stem , Early Branches and Elements Productive, controlling, destruction but the basic is still not understand for example if some born on

1 July 1991 10Am FeMale

so how do i know his year is which element and HS

i also did 60 years but still not understand it would be appricate if some share here or any video or book link

Thanks