Can you do SEO yourself? Of course you can! The internet is filled with free information that can teach you what you need to know to be able to do it.  Here are two pieces of content to start with:

Because there is so much information online, it can be overwhelming.  If you’re thinking about hiring an SEO agency, it’s best to hire multiple agencies and hear their take on SEO and what they would do to see if there are any common themes.  Reading a few beginner guides will also help you better understand them as well.