Generally speaking, there are 2 ways to transfer photos from computer to iPhone/iPad/iPod:
- Use iCloud, if your iPhone is under good Wi-Fi connection. Go to iCloud.com on your computer, sign the same Apple ID as your iPhone, then upload videos from your computer to iCloud. Finally you can download and view photos on your iPhone.
- Use iTunes, if you have USB cable. Connect your iPhone to computer first. Click "File > Add Files to Library" at the upper left corner of the window. Then select the photo files on your computer and add them to the library. Finally sync videos to iPhone.
Note: iTunes syncing process will erase unselected photos from your iPhone permanetly. Make sure you have a backup or sync with all wanted photos to iPhone.
There are two other options to transfer photos from computer to iPhone, including Dropbox and third party program. Read on it for more detailed steps: How to Transfer Photos from PC to iPhone?