I'm writing a book i need help do i get an agent?

i start to write a few months back something to do with real life and i realized the other nite if i put it into a book it would already be 100 pages .. its not done yet either its goin to be a really long book or cont into two books ... i was wondering how i go about getting it published ..??? i feel as if people would love to hear it, so what do i do?