There are two ways of doing this.
Firstly, every photo you upload will be entered into the monthly awards. You can select which theme (portrait, landscape or wildlife) you want to enter each photo into while uploading.
Secondly, you can resubmit a photo from your profile as long as it has not previously been a Finalist or a Winner. You can do this by selecting the photo from your profile, and selecting the ‘Submit Photo’ button.