Need data/mms setting for tmobile iphone 3gs on IOS 6.1.3?

[Terry]

I am unable to get to the correct setting option for this.
I go to settings/general/cellular/- and from there is the problem. I do not have the "cellular data network" option to add the APN.
all that is there is:
Cellular Data
Enable 3g
Data Roaming
use data for
Itunes
passbook updates