Adding Bootstrap inside functions.php

function reg_scripts() {
    wp_enqueue_style( 'bootstrapstyle', get_template_directory_uri() . '/css/bootstrap.min.css' );

    wp_enqueue_script( 'bootstrap-script', get_template_directory_uri() . '/js/bootstrap.min.js', array(), true );
}
add_action('wp_enqueue_scripts', 'reg_scripts');