You've just created your artwork and uploaded it into Fuel, but the mockup says that your print quality is poor at the size you want. In this case, the artwork DPI is too low. For a refresher about the artwork size needed for each item we offer, please see this page.
Here's how you can resize your artwork to ensure that the print will come out just right.
Open the art file in Adobe Photoshop and center the artwork on your screen. If you are using a laptop or smaller display you can use the Zoom tool to view the artwork. This tool can be found in the toolbar on the left side of the screen and is represented by a magnifying glass as pictured below.
With the tool selected, hold down the left mouse button and drag the mouse cursor to the left to zoom out and right to zoom in.
To resize the artwork, navigate to Image - > Image size to bring up the sizing control panel. Note: The image can be found in the upper left-hand corner of the screen.
The chain link icon highlighted by the blue arrow in the photo below constrains the aspect ratio of the artwork as the dimensions are changed. It is recommended you keep this setting on as it will prevent distortion by keeping the height and width proportional when resizing.
Before finalizing size changes, check the numerical value in the resolution box. Depending on how the image was made this value could range from 72PPI to 300PPI on average. As a general rule 300PPI is more appropriate for material that will be read close.
Do your happy dance because your file is now resized and safe to save.