You can attempt to do SEO on your website yourself, but you can also pay a professional to do it.
The first option is cheaper, of course, but it takes time to understand how SEO and algorithms work. It’s a slow learning curve with lots of research involved. Besides, you may still have to spend money on certain tools. The problem is they all promise you the world, but not all of them can deliver.
Paying a professional for SEO means relying on someone who already knows all these, someone who has the experience to make things happen much quicker.