HI Kim,
SEO is not a button or option to turn on I am afraid, its a big deal.
It is a massive area of an online business from the core structure of the site, the way its constructed, the size of the site, the domain, the domain age, the way the site is linked in internally and externally linked.
The content is always king and how that is structured with the amount of relevant information, the keywords in that content and the semantic markup of that content and its HTML. Things like one only heading 1 tag is only a smigden of the things to considert to get anywhere close to ranking.
New sites can take up to 6 months to properly assess where it naturally ranks and then work on changes and updates to get further. What the site is and the number of other sites in the same area will all factor in a sites ranking as well. Then you would also look at SEM which is the marketing of the website to achieve the best search ranking.
If your top on "Natural" searches your doing VERY well but you need to understand from the start that this is a very hard thing to achieve.
If you search something like "My site very specific wording thats unique to my site" then of course you will show up, but thats not how people search so keep that in mind.
In terms of Muse, Muse is a more simpler tool to build websites as graphic designers and like, it does not have that much SEO consideration, so this will never be able to achieve the heights your hoping for as a custom build site would be with good html markup and semantically correct. Such work creates the foundation for the site, its content and SEO.