Every element that can be placed on a page is accessible under the Build tab, from the menu on the left. To add an element to the page you are currently on, click on the Build tab, locate the element, drag and drop it at a desirable place. You will be automatically prompted to edit the element. Once the necessary changes are applied, just click outside of the element and the changes will be saved and ready to publish. If you need to edit the content again, click inside the element to open in-line editing options and load the right menu.
To locate the necessary element, you can select one of the available categories or use the Show dropdown to narrow down your search and filter out the elements, based on their utilisation. For quick and easy access to a certain element, you may as well use the search bar.
From the Build tab, you can as well install applications. The ones visualised with lower opacity and a green padlock are yet to be enabled. Selecting any of those, will prompt the installation pop-up window, for the respective app. Once activated, the application may now be placed on a page.
All other content elements are already enabled by default. More information regarding each category in the Build tab, can be located in the respective help article.