Open the file folder containing the images you want to use and select up to 10.
Drag and drop them into the space provided above.
Download the converted images.
That will depend on what sort of image your are working with. In summary, JPGs are better for photographs, while .png images work better for graphs and pics with text. If you are ever unsure and want to retain the quality of the image, the PNG is a safe choice as it can retain the sharpness and the readability of the text in the picture.
For printing, you want to go for higher quality, PNG will be the file type to use, due to their use of LZW compression, which means no quality will be lost as the file is shrunk. However, PNGs overall have a larger file size, so if you are sending files over the internet, and limited by the speed, then JPGs may be a faster option.