Welcome to Android Central! Have you already tried the APN settings provided by Consumer Cellular? Go to this support site and type "APN" in the Ask a Question box, then select the only result that comes up: https://www.consumercellular.com/Support/Knowledgebase
Also, which exact S4 variant do you have? Tell us the exact model number in Settings>About Phone. If the variant you have doesn't support the bands that Consumer Cellular uses, then no APN settings will work.