Yes it is needed to do seo separately as it is a time of core competition and you need to be on top results else you can not have more customers coming to your site.
Do it seperately. It starts with good keyword research and providing good quality content for your site
Think of it this way, the world wide web (www) is a like the universe vast , dangerous and gigantic! Now think of the earth as a search engine where Millions of humans(website) live and breath. This is where SEO comes in. This is your voice saying , hey earth can you hear me now? lmao
The most important features of SEO is to get more traffic from diverse sources and to get repetitive visitors. You can also try other SEO tools,they're useful too.