Possible Duplicate:
How can I configure my phone for MMS?
I am using a Samsung GT-I5503 and I can't send an mms. Where can I locate the mms settings so that I can configure it?
Settings >> Wireless & Networks >> Mobile Networks >> Access Point Names
That should list the APNs applicable/configured for your network; Once you select the APN entry (click on the name) you should be able to see/configure MMS.
Update: Here is another question on MMS configuration : How can I configure my phone for MMS?
