Cholzhauer,
Early Media is turned on by default and changing it is not a simple thing as you don't "normally" get to even see that field. If you want to check it to ensure that it is set to yes then go to your SIP Peer Trunk Group that is used for the SIP Trunk and then turn on On-Line Monitor under your View settings.
There is a field called Early Media Supported: Yes
Thanks,
TE