A great first step is to add a page.
Pages are your sites public facing web pages.
To add a page click on the Pages button and then click Create Page
PageBuilder's building blocks are the literal building blocks of your site.
A Page is made up of these building blocks. Add one by clicking on one.
Each one usually takes up one vertical block of space.
On each building block there is a round edit icon, click it to edit that sections options.
Each one has its own settings and fields. When you edit you will see the changes appear live above.
You can easily, rearrange, add or delete each sections blocks.
Once happy hit save at the bottom every-time you make a change.
Those changes will be made live once saved.
Once you have a page you are happy with add it to your sites navigation or link to it from a button.
Theme settings simply change the way your site looks.
These options can be found under the tab settings / theming.
Adding your logo to your header is a great first step.