Hover over the step by step to get the instructions: Please note that any program that allows you to correct brightness and contrast should work for this tutorial.
Image taken from InkaFinland etsy store
Step1: Try to find in the software of your preference something called Brightness and contrast. There you will be able to increase the brightness and the contrast of your product.
Remember always to keep a balance between how bright and vibrant your product should look. The idea is to increase the light without washing the colors of the photo.
Step 2: Increase the brightness of the product without exaggerating, if you have an image that looks too bright the buyer will feel that perhaps the image was edited too much and will doubt about the quality of the product. Always keep in mind that the product should look natural
If the software or online photo editor of your preference has the option to crop the image, you can choose to crop it a little. In that way all the space around the image will decrease and the buyer will see the image with more detail.