Follow this link to learn everything you need to know about applying for or renewing your passport: https://travel.state.gov/content/travel/en/passports/apply-renew-passport/how-to-apply.html
Important! If your current passport expires before November 7, 2021, you MUST apply for a new passport before going on this trip to Kenya in May. Kenya will not let you enter the country if your passport expires within 6 months of the trip. It can take several weeks to receive your passport, so whether you are renewing or applying for the first time, allow yourself plenty of time!
Passport and visa fees are your responsibility and are not included in the price of the trip.
VISA: Every person from the United States traveling to Kenya must have a visa to enter. You can apply for a single entry visa online at: http://evisa.go.ke/evisa.html The cost is $51. It takes just a couple of days to get your visa and it is good for 3 months. So for this trip, do not apply before March, 2021.