Lets assume schema name is my_data. If we want to avoid prefixing every table with my_data while creating a new table, we can set it in the search_path.
SET search_path TO my_data;
Now we can create a new table like this.
CREATE TABLE courses (
id SERIAL PRIMARY KEY,
course_name TEXT
);
By using the above code, courses table will be created in my_data by default.