Back when the thingy52 was released there was a specific Thingy52 SDK and a thingy app. You can find the SDK here. However as it was it's own thing it has not been touch for many years and since then we have changed our primary SDK to Zephyr. The thingy52 is supported in Zephyr but you need a external debugger/programmer to program the thingy as it do not have an onboard debugger.
If you are new to NCS I would highly recommend you to go through our nRF Connect fundamentals course to get an introduction to our SDK and Zephyr. I would also strongly recommend that you use a development kit for learning rather then a thingy. The thingy is limited in terms of GPIO and the lack of debugger makes it more difficult to work with.
