test.php

<div class="wp-social-box">
	<h3>Xpert Optin Option</h3>
	<form class="optin-form" method="post">
		<div class="width-70">
		   <label for="title">On Page Load</label>
		   <input type="checkbox" name="block_one" value="onloadValue"></input>
		</div>

		<div class="width-70">		
			<label for="block_one_position">Select</label>
			<select name="block_one_position" id="block_one_position">
				<option value="top">Top</option>
				<option value="middle">Middle</option>
				<option value="bottom">Bottom</option>
			</select>
		</div>
		<div class="modal-footer">
		 <p class="submit"><input type="submit" name="submit" id="submit" class="button button-primary" value="Save Changes"  /></p>    
		</div>
	</form>
</div>
<?php



if(isset($_POST['block_one']) && !empty($_POST['block_one'])) {
	$onLoad = $_POST['block_one'];
	if($onLoad == 'onloadValue'){
        wp_enqueue_script('app-optin-js', plugins_url('assets/js/app_optin.js', __FILE__), array('jquery'));
       }
}

function load_script() {
    if(isset($_POST['block_one']) && !empty($_POST['block_one'])) {
        $onLoad = $_POST['block_one'];
        if($onLoad == 'onloadValue'){
            wp_enqueue_script('app-optin-js', plugins_url('assets/js/app_optin.js', __FILE__), array('jquery'));
        }
    }
}

add_action( 'wp_enqueue_scripts', 'load_script' );