Canva is an excellent tool for creating designs, but other graphic software such as GIMP, KRITA, or photoshop will also work.
You need to use the correct sublimation ink and transfer paper to print your design. Only a printer rated for sublimation will work correctly with these inks and papers.
Use a heat press to transfer the image from the paper to your object. The process is similar to a fake tattoo, which uses water to transfer the image to your skin.