How to save DVD files onto my computer than transfer them onto iTunes?

I recently bought Green Day's "Bullet in a Bible" and "Awesome As ***" as well as All Time Low's "Straight to DVD." Since I have the physical copies, I would like to save the DVD files onto my computer so that I could transfer them onto iTunes and eventually sync them onto my iPhone. I just can't figure it out.

You can use dvd ripper software to rip DVD to video for your iPhone
share a video on how to rip DVD to iPhone

You may try Any DVD Cloner.

It supports to rip DVD to iPod/iPhone.

You need to convert DVD movies to video files formats on computer firstly. For your iphone, things would be much easier. You can follow one guide about it. You can search" how to rip and convert DVD to iPod/iPhone 4S with DVD Ripper" and follow step by step. You can do it if you do the same as the guide.