Q: how do I get photos from my apple computer to my iPhone

IF you only want to sync selected photos, create a folder with the photos that you want to transfer to the phone and then sync that folder of photos using iTunes.

Sync photos from your computer to your iOS device using iTunes - Apple Support

You could also use a third party WiFi transfer app like this. There are others in the App Store.

http://www.wirelesstransferapp.com/

Another way to do it if there are only a few to transfer is to email them to yourself. DropBox is another way to get them from the computer to the phone.