Hi Victoria,
In order to wipe your SD from this model camera you must turn on the camera with the SD Card correctly inserted and then press the menu button. Then scroll to the right so that the wrench and the hammer tab is now highlighted. Now scroll down to "Format..." and select it. The menu will now prompt you to format the memory card, press OK twice and your memory card will be wiped.
For any further issues visit our Canon PowerShot A2500 [[Canon PowerShot A2500 Troubleshooting|TroubleShooting]] guide. Where there are guides for several other common problems.
Hope this helps,
-James