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There are many ways to scan. The easiest method is by using Apple's Image Capture application. Go to Applications folder and you will find the Image Capture application in there. Open it and you will find your printer on the left side under Devices. Click it and click Scan.
Another way is, open Preview application from Applications. Click on File menu and select Import from Scanner. Then follow the onscreen instructions to scan.
If you have any difficulty, please let me know and I will walk you through the steps.