Open your Reason software and move your mouse to a blank area under the music racks on the main page. Right-click anywhere in the blank area, which will bring you to the "Context Menu." Select "Create Instrument" when the drop-down menu appears.
Keep in mind that once you click on "Create Instrument," another drop-down menu will appear. Select "Refill Packages" page. Remember that there are already two pre-installed refills that come with your Reason software. Add another instrument by browsing through the "Refill Packages" until you see the one you want to add. Select the refill, then choose the patch that contains the instrument that you want to add.
Click on the patch that contains the instrument you would like to include in your project. Wait while your patch downloads the instrument. Return the to main page, and check your music racks. Your new instrument will appear in the next accessible rack slot.