How can i implement “select from existing tags” front end posting?

Hy,on the bottom of Tags: I want to add something to be able to select from existing tags.

Users can make new tags but I want them to be able to choose from existings tags.

This is what I extract from WP Core, Is there any chance I use these codes? http://textuploader.com/5w9pf

Here it's a image of what I want:
[Attachament at bottom]

Here it's php and html code :

case "window-image":
                $format = 'image';
                $title = esc_html($_POST['title_image']);
                $tags = $_POST['tags_image'];
                $comments = isset($_POST['comments_image']) ? 1 : 0;
                $user_id = $id;

                if(($_FILES['file']['error'] != 0) || $title == '' || str_word_count($tags) < 3) {
    				wp_redirect(home_url('/') . '?posterror=1');
    			exit;
    			}         

    			$post = array(
    			  'comment_status' => $comment_status,
    			  'ping_status'    => 'open',
    		      'post_author'    => $user_id,
    		      'post_content'   => '',
    		      'post_status'    => $status,
    		      'post_title'     => $title,
    		      'post_type'      => 'post',
    		     );
    		    $post_id = wp_insert_post($post);

    	#Upload and Create attachment
    		if (!function_exists('wp_generate_attachment_metadata')){
                require_once(ABSPATH . "wp-admin" . '/includes/image.php');
                require_once(ABSPATH . "wp-admin" . '/includes/file.php');
                require_once(ABSPATH . "wp-admin" . '/includes/media.php');
            }
    			$upload = wp_upload_bits( $_FILES['file']['name'], null, file_get_contents( $_FILES['file']['tmp_name'] ) );
    			$wp_filetype = wp_check_filetype( basename( $upload['file'] ), null );
    			$check = getimagesize($_FILES["file"]["tmp_name"]);
    			if($check !== false) {
    			$uploadOk = 1;
    				} else {
    				echo "File is not an image.";
    			$uploadOk = 0;
    				wp_trash_post( $post_id  );
    			}

    			$wp_upload_dir = wp_upload_dir();
    			$attachment = array(
    				'guid' => $wp_upload_dir['baseurl'] . _wp_relative_upload_path( $upload['file'] ),
    				'post_mime_type' => $wp_filetype['type'],
    				'post_title' => preg_replace('/\.[^.]+$/', '', basename( $upload['file'] )),
    				'post_content' => '',
    				'post_author' => $user_id,
    				'post_status' => 'inherit'
    			);
    			$attach_id = wp_insert_attachment( $attachment, $upload['file'], $post_id );
    			require_once(ABSPATH . 'wp-admin/includes/image.php');
    			$attach_data = wp_generate_attachment_metadata( $attach_id, $upload['file'] );
    			wp_update_attachment_metadata( $attach_id, $attach_data );
    	#Upload and Create attachment

    	#Use attachment
    			update_post_meta( $post_id, '_thumbnail_id', $attach_id );
    	#Use attachment
                break;
------------------------------------------------------- HTML ----------------------------------------------------
<div class="post-window window-image">
        <div class="window-left">
        <textarea name="title_image" class="form-control" rows="1" placeholder="<?php _e('Post title', 'Aruna');?>"></textarea>
    	Memes and GIFs -- Max size: 10MB
    	<input type="file" class="upload" name="file" accept="image/*"/>
    	<hr>
    	<center><button type="button" class="btn btn-danger" data-toggle="collapse" data-target="#Info-ImagePost">Please read before posting</button></center>
    	<div id="Info-ImagePost" class="collapse">
    	<div class="alert alert-info">
    	<em><p>If you dont know how to post please take a look at FAQ page: <a href="http://www.9tanks.com/faq/"><button type="button" class="btn btn-success btn-xs">FAQ</button></a></p></em>
    	<em><p>If your post doesnt show or has a problem please report the post and in the shortest time we will resolve or you can delete your own post and try again</p></em>
    	</div>
    	</div>
    	</div>
        <aside>
    <div class="outer">
        <div class="inner">
    <div class="tags-wrap">
        <h3><?php _e('Tags', 'Aruna');?>:</h3>
    	<p><?php _e('Please write at least 3 tags. Ex: IS-4,El Halluf,Failshot');?></p>
        <input name="tags_image" class="tags-selector" value="" />
    </div>
    </aside>
    </div>