Each situation will be different so we recommend calling or sending a picture of your pool to email@example.com so we can help you find the best solution.
Place a 4x4 pressure-treated post at least 1/3 of the way into the ground and ensure the top of the post is level with the top of the pool.
Next, drill a 1-inch hole in the center of the post at least 3" deep and glue or epoxy the plate into the hole and let cure.
Installation should be within 1-2 feet and vertical with the side of the above ground pool.
Here's a document that shows one possible install method that works for most situations.