Some of the best design programs to use are from the Adobe Creative Suite they include Photoshop, llustrator & InDesign, they do require a level of skill to use these however free templates can be found online as great starting points. You can get a trial on the Adobe Suite for the purpose of creating your design.
You can also use Microsoft Word, Publisher, & PowerPoint. Just save/export your file as a PDF or JPEG before you upload your artwork to our site.