The Blocks manager panel, which can be reached by going to Admin menu > Site building > Blocks, is the main control panel for all blocks.
This panel can be very large and intimidating to new users, so we'll take some time to cover the main features of it.
The Blocks manager has several yellow blocks scattered around the screen. These indicate the different regions that are available for block placement.
A series of tabs appears at the top of the panel with the names of all enabled themes on the site. These tabs do not change the theme, they simply allow you to view the block layout when different themes are enabled.
The table in the center of the Blocks manager contains two main sections: Enabled and Disabled. Within the Enabled section are sub-sections that correspond with the yellow region indicators on the panel. When you place a block within one of these sub-sections, it will show in the matching region when saved.
To configure a specific block, click on its configure link. This will redirect you into that block's specific configuration panel.