You have successfully installed the Lambda Blog Platform. It is like any other blogging platform except that it is made to be 100% scalable and 0% maintanence. All components of LBP are developed on Amazon Web Services which means that you don't have to worry about servers.
To enter admin section visit /admin and enter the password that was given to you during the installation. If you forgot to take note, you can see it in your AWS Console under API Gateway -> APIs -> [your blog api] -> Stages -> Prod -> Stage Variables -> admin_pass.
In the admin section you can write your blog posts, set up your categories and tweak some settings as well as change the look of the current template. This blog is not meant to be a CMS and some basic programming knowledge (HTML, CSS and JS) is recommended for operating it beyond managing it in admin panel. If you want for example to change the front page template you have to create a new folder in /lambdas/templates and make new template files. LBP uses doT.js as a templating engine so it is a good idea that you get familiar wit it.
You can learn more about working with LBP here.