How to delete photos off iPhone 4s?

I have an iPhone 4s. I downloaded some pictures to my phone from my email and now I can't delete them it seems without restoring my phone. Is there a way to delete the photos without restoring my phone?

There should be an icon in your photos app in the top right that has the box with the arrow coming out of it. Click that and select any photo you want to delete, After that press delete in the bottom right.