How to delete pictures on my iPhone?

I put pictures on my phone from my computer a year ago, and now I can't delete them off my phone. I've never had iTunes on my computer, so I did it straight through the files on my computer. Now I can't delete them on my phone and they don't show up on my computer when I plug it in.

Click the trash can. It will ask, "Are you sure you want to delete this?" and you need to click "Yes". If you Click "No", then it will go back to the menu

Woah! I'm so techy! The world = *mindblown*

Follow the below points…

Step 1
Connect your iPhone to your computer and run iTunes.

Step 2
Click the iPhone's name listed under "Devices" on the left side of iTunes.

Step 3
Click "Photos" above the center panel in iTunes. Syncing options appear in the center panel.

Step 4
Click the drop-down field next to "Sync Photos From" and choose the source containing the photos you want to delete, such as your "My Pictures" folder or "Photoshop Elements."

Step 5
Click "Selected Albums." Albums associated with your chosen photo source appear below.

Step 6
Remove the checks next to the photo albums you want to delete from the iPhone.

Step 7
Click "Apply" in the lower right.