As mentioned in the previous post, you can get one on Amazon. I purchased mine at Publix.
SunPass is Florida's system and will also work in parts of Georgia. EZPass is used in the northern states. The SunPass device will only work on SunPass roads. The SunPass PRO device will also work on the EZPass roads. Not surprisingly, the SunPass PRO device itself costs a little more.
An important step is creating an account, providing funds (typically a credit card) and linking the device to the account.
https://www.sunpass.com/en/home/index.shtml and
Floridasturnpike.com have all the information you need. My account is set to automatically add $10 when the balance gets below $7
Once the device is registered to your account, the account is funded, and the device is installed in your vehicle you use the SunPass/EPass lanes with no need to stop or even slow down on the sections I have traveled.
EPass is a similar device from another tolling authority in Florida. I believe EPass is equivalent to SunPass and EPass UNI is equivalent to SunPass PRO.