First and foremost, your Net 10 device will work on Simple Mobile plans if and only if you have an unlocked GSM device.
Click here to see which carriers your phone will work with
Before you switch, make sure your device is unlocked and you have no outstanding fees on your device. If the device is unlocked, compatible and you have no outstanding fees then you are ready to switch.
Click here to Compare Simple Mobile Plans
Find a plan you are interested in and then purchase it. Find the correct size Simple Mobile SIM card and plug it into your device to activate.
To keep your options open, just know your Net10 device is compatible with many carriers! Its software technology is able to be compatible with both different types of software on the market, giving you full versatility - you do need to check whether your phone is GSM or CDMA
Click here to Compare all BYO Net10 options
Here are some carriers from that search results page that might be beneficial to you and your switch. Even if you have your heart set on Simple Mobile, its still good to know what other options are out there :)