I have 23 years experience as a p&c agent i was an istant to a broker i would like to open my own p&c agenc?

how di i do this in iowa i heard it was hard to get appointed with carriers since i dont have a book of business which companies should i try to contact im sure many clients from captive agency would join me if i could get some major carriers please help i am thankful for any help god bless, 23 years of experince should help me to get in with major companys iwould hope need some guidance from someone who has the knowledge of this