First you need to import the video to iTunes. Open the Video folder, click and Drag the Video to iTunes you don’t have to put the video at any special location, just put the video anywhere while iTunes running.
In iTunes Upper left coroner select the movie icon then click on home videos.
Your Video will be there in home videos. Next make sure your iPhone is connected to your computer then drag the video in to the Phone icon located at the top left corner.
Now you can see in the middle bar on top, the video will automatically syncing.
After the Process completed, Open Video app on your iPhone and you can see your Video waiting for you to play.