Creating a Publishing Site Collection
To create a new Publishing Site Collection, go to Admin –> SharePoint –> Site Collections and click on the New Private Site Collection button
Now that you have a Publishing Site, you can start to customize it with your new Master Page. Your default home page will look like this:
The Design Manager
If you click on “Design your site”, this will bring you to SharePoint 2013’s new Design Manager:
You can also reach this screen by clicking on the settings menu at the top right hand of the page and clicking on Design Manager
Mapping to the Master Page Directory
Click on Edit Master Pages and you will see a screen like this:
To Convert an HTML file to a SharePoint master page. Click on that link and you will see this dialogue box:
When you click on this you will access the same master page library that is used by the Design Manager.
If you click on files you can then upload documents and create folders through the browser UI.