Sharepoint 2013 allows branding on the portal. With this feature, you can clothe your html pages on the portal to get new views. If you have defined the site as a Team site when creating the site, you need to make some adjustments to enable this feature.

Settings / Site Settings on site navigation first

We come to Site collection features on the screen

You need to enable the Sharepoint Server Publishing Engine collection.

When this feature is enabled, the Design Manager in Site Settings will appear

We launch the Manage site properties option

Enable Sharepoint Server Publishing

Now you can see the Design Manager button in the menu that appears when you press Settings.

I hope this simple tip is useful for you.