Why can't I send or receive mms on my Sprint SPH-L520 ported to Straight Talk?

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AC Question

Can't send or recieve mms on my Sprint SPH-L520 ported to Straight Talk

I cannot send or receive mms on my Sprint SPH-L520 ported to Straight Talk. I have tried to find how to get to My APN settings but cannot even find it. It is not the usual way through Settings. I cannot update my phone over the air update, it just disconnects. I cannot update my software. It will download but not install on my phone. It just shows " Error ". I have tried Straight Talk online and The Customer service over the phone. After an hour on the phone they decided that they cannot help me. I am open to all ideas but please make it simple for an old guy. Thanks.