Envato Sites websites are made with building blocks. A "block" is any combination of elements like headings, text, images, videos, buttons, etc.
All of the website's blocks can be edited so you can add your content.
Firstly, ensure you are on the Build page:

Scroll over the block you want to edit, update or delete. Three buttons will appear in the top right hand corner of the block*.
Note: Different types of blocks provide different editing options.
Let's see an example using a Header block.
Edit Toolbar
In a Header, the Edit toolbar has options for:
- Updating or deleting heading and subheading
- Replacing the demonstration logo
- Editing the Navigation links and the Social Media icons

Layout Toolbar
The header block's Layout toolbar has the option to switch the content within the block to a different layout.

Note: Not all blocks will have this option.
Settings Toolbar
The header block's Settings toolbar has options for changing design settings like:
- Changing the background color based on your site color palette
- Replacing the white background with an image
- Enabling background patterns
- Enabling the blocks' full height
- Advanced options (eg. the block's URL)

*Don't see these options when editing your website? You could be using one of Envato Sites' older website templates. Get in touch if you'd like more information!