Q: How do I start an group conversation on iOS 8

The same way as IOS 7.

iOS: Understanding group messaging  Sorry, I thought you were a previous user.

Ok, the link I provide shows you how.

Message - type in the names of the contacts you want to send a group message to or hit the plus sign and add people.

nascarfan22 wrote:

 

How do I do that I am new to the iPhone

Based on your info you've at least had the iphone for 4 months and have been on IOS 7.

Did you not send group message while on IOS 7?

iOS: Using Messages

iOS: Troubleshooting Messages