After developing a website, you need to work with it. Otherwise, all the resources spent on development will not be recouped.
There are three ways to effectively attract visitors to your website: SEO promotion, contextual advertising, SMM promotion. Each of them has its characteristics, difficulties, and advantages in implementation.
In any case, after development, you should not allow a situation where the website is dead weight and wait for a miracle to come. A website is a great tool for increasing sales, but it is not able to work on its own.