Navigate to the page on which you wish to place a symbol.
1. Select the Modify button in the top right cornerof the page.
2. On the dialog that opens, select Modify.
3. Select in-between the buttons so that you're choosing the background of the page.
4. The Properties panel will appear.
5. Choose the blue Select button beside Symbol.
6. Select the symbol you wish to use as the background of the page.
7. Choose the Select button.
8. When satisfied with the changes select the green check mark in the top-right corner to exit your edit