how can i send photos to my friends Macbook using my Macbook iMessage App

How can i send photos to my friend who is chatting with me on iMessage ?

My friend had uploaded his photo in his iMessenger app but i am able to see his profile photo on my iMessage app ?

As i am a beginner in using Macbook and i was using Windows 8.1 pro ,so thats why i am facing some issues.

Please Help me.

Thanking You