How or where to edit a video?

I would like to edit a video from my iphone.
i saved it on my computer and it is sideways i would like to rotate the video
where can i do that?

also resize the video

The iPhone 4 and iPhone 3GS aren't the first smartphones that can record video. The twist that Apple gave them is that not only can you record video, but you can also edit videos and share them via email, SMS, or YouTube.

Because the iPhone 4 & 3GS are phones, don't expect a full-featured video editor. Video editors that include intensive features like effects and sound editing require complex, and often-expensive, desktop video editing programs. That's just not possible on a phone with a touch interface. What the editor will let you do is trim and snip videos, so you can save just the good part of a recording.
Here's How:

To edit a video, you'll of course need to have recorded video on your iPhone. Once you've done that, you'll need to go to your Camera Roll to edit (if you just took the video, simply click the box in the lower left corner. If you're looking to edit a video taken earlier, tap on the Photos app, then Camera Roll, and find the video you want to edit).
At the top of the window, you'll see a timeline bar showing frames from throughout your video. A small silver bar rests on top of the timeline bar. You can tap and drag the silver bar to move forward and backward throughout the video. This lets you quickly get to the part of the video you want to edit.
To edit the video - which, remember, means just trimming footage off one end or the other - tap and hold either end of the timeline bar (there are two little lines at each end of the bar). At this point, the bar will turn yellow and a button labeled "trim" will appear above the timeline bar.

Drag either end of the yellow bar to cut out the parts of the video you don't want to save. The section of the video shown within the yellow bar is what you'll be saving.

When you're happy with your selection, tap the "Trim" button at the top right. You'll be given two options: Trim Original or Save as New Clip. If you choose Trim Original, you cut from the original video and will permanently delete the sections you remove. If you choose this, be sure you're making the right decision: there's no undoing it; the video will be gone.

for more flexibility, choose Save as New Clip. This will save the trimmed version of the video as a new file on your iPhone, allowing you to view the new clip, but also return to the old one to make other edits if you're not happy with your handiwork.

Once you've created and saved the clip as you want it, you've got four options for what to do with it. You can simply save it and then sync it to your computer as normal. But, if you tap the arrow button at the bottom left of the screen, you'll have three options: Email Video, MMS, or Send to YouTube.

Choosing email will email the video to any address from your phone. Choosing MMS will send the video as a text message. Send to YouTube will automatically format the video for YouTube and post it to your account (this requires a YouTube account) for all the world to see.

On your PC you can use this app Free video flip and rotate http://www.dvdvideosoft.com/products/dvd/Free-Video-Flip-and-Rotate.htm