Inserting array into postgresql

I want to insert array of id's to a filed but while creating table i used int and it has the reference of another table now how can i store array value to the specific field?

 db.query('CREATE TABLE IF NOT EXISTS departments_users(_id SERIAL NOT NULL UNIQUE PRIMARY KEY,user_id int REFERENCES companyUser ON DELETE CASCADE,department_id int REFERENCES departments ON DELETE CASCADE)');

    exports.addCompanyUser = function(data, callback) {
     db.query('INSERT INTO departments_users(user_id,department_id) VALUES($1,$2) RETURNING *', [companyuseraccess.rows[0]._id, data.department]).then(function(departments_users) {
    })
    }

via schedular