Once the plugin is installed, Spreadsheet is available as a macro in a Confluence page.
When your are creating or editing a page, if you want to add a Spreadsheet, simply follow these instructions:
Click "+" in the action bar to open the "Insert more content" menu. Then click on "Other macros".
In the search box at the upper-right start typing "Spreadsheet", when you see the Spreadsheet macro, select it.
From here you can choose to start a new document, use or copy an existing document, or import an existing Spreadsheet/Excel document.
Optionally, you can trigger this screen (below) by typing directly "{spreadsheets" in your page to activate Confluence's macro insertion syntax and selecting the Spreadsheets option.
Saving and exiting Spreadsheets
To save your document you must give it a name.
Once your document has a name, save it by clicking the Save icon in the editor toolbar OR clicking on the validation icon in the top-right of the header bar.
Each spreadsheet is saved as an attachment. Learn more...
After you've named and saved your document click the Close icon in the top-right of the header bar to start editing.