Hi Tom,
The "check engine" light, more commonly referred to in the industry as the Malfunction Indicator Light (MIL) comes on when the engine computer detects a fault condition. So the light coming on, even if it doesn't stay on, means the computer has seen an issue. Lucky for us, whenever it does it records the problem in the form of what's called a DTC, or Diagnostic Trouble Code, or just trouble code for short. Those codes consist of a single letter followed by four numeric digits.
Although some higher end cars' dash is capable of displaying those codes for you, most of the time you need a scanner to plug into the On Board Diagnostics (OBD-II) port to read out the codes. You can buy a very inexpensive bluetooth scanner that works with a free app on your phone online for under $5 that will serve to get you the code or codes. Here in the US most auto parts stores will take their scanner out to your car and hook it up for free, giving you the codes it finds.
Those codes will most likely indicate what's causing the problem with your Kia. Generally what you'll do is put the year, make and model into the search engine, along with the particular trouble code(s) you have, and most of the time the results will give you a good idea of what you need to look at to fix the problem.
Of course, once you have the codes you can always come back here and add them to your question and we'll see what we can do to help you figure out what's going on with your car.