Hi Gladys,
I love being a Florida Resident Seasonal Passholder and have taken advantage of the monthly payment program since it began three years ago. It's a great additional benefit.
When the program initially began, the monthly payment option was available online only, but it has since been expanded so that you can buy tickets using the payment option at any Walt Disney World ticket window. Here's the link to the Disney Parks Blog announcement of the
monthly payment program, if you'd like to see the details.
Your tickets will be good for one year from the date of first use, regardless of when you buy them. So you can purchase online in advance without worry that you will waste any days of your pass. When you buy online, you get a voucher to exchange at any Walt Disney World ticket window for your passes.
Whether you purchase online or in person, every adult activating a pass will need to show
proof of Florida residency.
I hope that clarifies things for you. And I hope you and your family get as much enjoyment from your seasonal passes as we have from ours over the past 15 years.
Wilma