Q: How to transfer an iphoto pic from macbook pro to iphone 5s

You can do it several ways:

via usb cable using iTunes: Sync photos to your iPhone, iPad, and iPod touch in iTunes - Apple Support

via 3rd party apps such as http://www.photosync-app.com

via Photo Stream: My Photo Stream FAQ - Apple Support

The easiest way is via iCloud photos, if you use iOS 8.2 or later and OS X 10.3 or later. 

If not, you do this by syncing via iTunes -go to the Photos page of your device connected to iTunes to select what to sync.

I used to do that by creating a folder in iPhoto with several albums in it. Then I added the photos I wanted to go to my iPhone into those albums and synced the entire folder. If you only have a few photos and don't need them in separate albums on the phone then you could just create a single album in iPhoto for photos that you want to sync. It works very well as if you later want to add more photos to your phone, you simply add them to the previously created album(s) and sync again.