I wanted to make sure you are entered in my blast from the past challenge so I am going to try to explain how to enter a tag on a photo.
In your gallery, if you click on the photo of your project it should bring up to a screen where you have a few options you can do with your photo.
One of those options is to add a tag. Below the picture on the right side is an option called 'Edit Your Tag', if you click on this option it will bring up a small box that you can enter tags in. This is where you want to enter the tags for any of the challenges you enter. This will make sure you get in the drawings for the free stamp set. Please let me know if you have any problems and I will try to explain it better for you.