How do I get to the settings to make No APN specified on the device go away on my ZTE Cell Phone?

[AC Question]

how do i get to the settings to make "No APN specified on the device" go away on my ZTE Cell Phone?

"No APN specified on the device. keeps popping up on my phone and staying there making it difficult to to text and send pictures or even play games on my phone. I took my phone to my Boost Mobile carrier provider and they did something to make it go away but it just came right back. Where do I go to in my settings to create