Depending on the make and model of your printer, you will need to either look in the user manual that came with your printer or click on the different printer "features," "preferences," or "set up" configurations.
As shown to the left, after opening the reversed image, I clicked on File, and selected Print. Once the print pop-up window appears, I clicked on a "Page Layout" option.
This option allowed me to select "Mirror" (which is shown here by the image of a computer screen, an iron-on transfer paper, and an imprinted T-shirt).
Depending on your printer, you may have an option for "Transfers" or "Reverse Imaging"---something that will indicate that when the page prints, it will print in reverse.
Once you have re-flipped the image and printed it, be sure to re-set your printer settings for normal printing.
After you have downloaded the reversed image, open it in Microsoft Paint (as you can see here, the colored image of a birthday cake with an 8 on it and the words inside the dotted line are reversed; the instructions for cutting out the image above are not reversed).
Click on Image, and then click on Flip/Rotate.
Go to How To Use Iron-On Transfer Paper for tips on using iron-on transfer paper.
After you have downloaded the free printable iron-on transfer determine if it has already been flipped. If you have transfer paper that requires the image to be flipped, then you can simply print on the transfer paper, following the instructions given.
If you have transfer paper that requires the image not to be flipped, then you will need to re-flip it. Re-flip the image using only one of these options, not both.