Ericaceous trees and shrubs are those that belong to the plant family Ericaceae, heaths and heathers. They all need acidic soil to grow. So ericaceous soil is just a fancy term for acidic soil. You don't have to "get" it, you just have to acidify the soil you have.
Blueberries need soil that is quite acid -- between pH 4 to 5.5. To start with you need to know what the pH (acidity) of your soil is. You can get pH meters or test strips. Are your blueberry bushes going in the ground or in containers? If your natural soil is pH 7 or above (neutral to alkaline), you will be better off growing them in large containers. Anything you do to acidify the soil planting them in the ground will be constantly neutralized by contact with the surrounding soil.
Blueberries want rich, organic soil as well as acidic.
Welcome to the Forum! When you tell us what your soil pH is, we will tell you what to do from there!