You have a few options here:
Register for a post office box by clicking here (https://reg.usps.com/register?app=POBO&appURL=https://poboxes.usps.com:443/poboxonline%2Fpages%2FmyAccount.do). Alternatively, you can fill out and take the paper form (https://about.usps.com/forms/ps1093.pdf) to your local post office.
Use a coworking space. This is probably the most expensive option, but it includes more than just a mailing address. A coworking space is usually full of entrepreneurs, which could end up being a valuable networking and learning opportunity for you.
There are a plethora of online business management companies who offer mailing address services.
Hire an attorney during the formation process. An attorney may use his or her own address as your business address on formation forms.
LawTrades (www.lawtrades.com) is a site created by entrepreneurs for entrepreneurs, where our mission to help startups find affordable legal services. Just tell it what you need, and it'll introduce you a handful of vetted startup lawyers. Then, compare by price/reviews/professional chemistry and simply hire the best lawyer.