job_bm_company_submitted

add_action('job_bm_company_submit_form', 'job_bm_company_submit_form_19082019');

function job_bm_company_submit_form_19082019(){

    ?>
    <div class="form-field-wrap">
        <div class="field-title"><?php echo __('Custom input field','job-board-manager-company-profile'); ?></div>
        <div class="field-input">
            <input placeholder="" type="text" value="" name="custom_input">
            <p class="field-details"><?php echo __('Custom input details.','job-board-manager-company-profile'); ?>
            </p>
        </div>
    </div>
    <?php

}

validated data and error

add_filter('job_bm_company_submit_errors','job_bm_company_submit_errors_19082019', 90,2);

function job_bm_company_submit_errors_19082019( $error, $post_data){

    if(empty($post_data['custom_input'])){

        $error->add( 'custom_input', __( 'ERROR: Custom input is empty.', 'job-board-manager-company-profile' ) );
    }

    return $error;

}

Save data after validated

add_action('job_bm_company_submitted', 'job_bm_company_submitted_19082019');

function job_bm_company_submitted_19082019($company_id, $post_data){


    // save custom input values
    $custom_input = isset($post_data['custom_input']) ? sanitize_text_field($post_data['custom_input']) : "";
    update_post_meta($company_id, 'custom_input', $custom_input);


}