How to customize SQL query

I have 1 module with model, resource model and collection. Now I can get data with SQL query: SELECT main_table.* FROM table_abc AS main_table; I want to customize this query by adding WHERE clause (for example: WHERE 3 = 3). How can I do that? I tried to add $this->getSelect()->where('3 = ?', 3); into _initSelect method of collection but It didn't work (When I see SQL log I realize SQL not change)

Here is my full code (Collection class):

<?php

namespace ScPortal\SubscriptionItems\Model\ResourceModel\SubscriptionItems;
use Zend\Log\Writer\Stream;
use Zend\Log\Logger;


/**
 * Class Collection
 *
 * @package ScPortal\SubscriptionItems\Model\ResourceModel\SubscriptionItems
 */
class Collection extends \Magento\Framework\Model\ResourceModel\Db\Collection\AbstractCollection
{
    /**
     * @var string
     */
    protected $_idFieldName = 'subscription_items_id';

    /**
     * Define resource model
     *
     * @return void
     */
    protected function _construct()
    {
        $this->_init(
            \ScPortal\SubscriptionItems\Model\SubscriptionItems::class,
            \ScPortal\SubscriptionItems\Model\ResourceModel\SubscriptionItems::class
        );
    }

    protected function _initSelect()
    {
        parent::_initSelect();
        $this->getSelect()->where('3 = ?', 3);
    }
}