If your page type is Custom Plus or Standard, then you are able to add content blocks to the page and update it within Composer Web.
There are 4 types of content blocks you can add to your pages, using a combination of these content blocks you can build up the contents of the page
|Content||This is for adding text to a page|
|Single Image||This is to add a single image to a page|
|Picture Grid||This is to add multiple images to a page, to form a grid or slider for example|
|Snippet / Embed Code||This is to embed HTML code within your page|