Why can't I delete pictures off of my iPhone?

I got an iPhone yesterday and was syncing it up and it asked me if I wanted to sync my pictures from the computer to my iPod and my dad accidentally clicked yes but I told him I didn't want those pics so he canceled it but it put the pics on my phone anyways! I went in the album and selected all the pics but it doesn't give me the option to delete them. They're taking up space and I don't want them. Does anyone know how to remove them? And please try to explain in a way that a 14 year old would understand ^_^ My dad tried to mess around with it and figure it out but he just ended up stressed out saying he'd do it later, but I'm very impatient and I've taken it upon myself to fix it.

You need to have ios 5.1.1 or higher to deleter you photos from photo stream! Go to setting-general-about and check what version you have. If you have lower than 5.1.1, you can't delete photos from photo stream. Or unable photo stream on setting.

1. Plug your iPhone into the computer with the USB cord.
2.press the start button on the bottom right corner.
3. Click on my computer.
4. Open your iPhone drive.
5. Look for the folder that has the pictures then just delete.