Q.How Do I Fertilize Older Apple Trees.
My wife and I purchased a farmette that had four older apple trees and we didn`t get any apples until this year and this year they were just loaded but the old owners never fertilized anything before

Certified GKH Gardening Expert
Generally, you will want to know what is lacking in soil before you apply anything. Getting a soil test will be your first step. You can have this done, or you can do it yourself.
This will help you find your local extension service:
https://www.gardeningknowhow.com/extension-search
These articles will help you to test your soil for yourself:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/test-soil-for-pests-and-diseases.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/making-sure-soil-drains-well.htm
This collection of articles will help you with apple tree care: