To apply pesticides you must have a pesticide license. I noticed on your profile your only 17. So I don't know if you can be licensed or not. Contact your Department of Agriculture Trade and Consumer Protection Office(DATCP). They should be able to tell you what you need to do in your state to get certified and licensed. Here in WI they offer a class followed by the exam or you can do a home study and then take the exam. I did the home study. I read the book on and off when I had time. It took me about 5 months until I thought I was ready to take the exam. There is alot of stuff you need to know.
Here in WI the certificate is good for 5 years, but the license is only good for 1 year. So every year you have to reaplly for the license but only have to take the test every 5 years. I don't know if it's the same in other states or not. Because I am self employed my bussiness needs to be licensed($125 a year) and I need to be licensed($60 a year)
As far as a program to follow. Go to your local supplier (lesco) or whoever you have in your area and they should be able to set you up with a program.