All STC chips are 8051 core derivatives, they cannot be programmed using Arduino IDE. You can compile C based programs for the device with SDCC (public domain) and download with a serial device, these days that means a USB to serial converter plus a switch and some diodes which is well documented in the STC literature. Yes, you could use an Arduino for its USB to serial converter but that's more expensive and harder to use than say a FT232 or CH340 breakout board.
All STC chips have a pre-installed, non-erasable bootloader and STC publishes their own downloader software STC-ISP, it's free but it's a Windows only program. There is also a public domain program called STCGAL which allows you to download programs using Linux or OSX.
If you don't know the 8051, start here:
You will not be able to use the IDE for STC parts but you can learn the 8051 basics with it and develop and test subroutines with the simulator.
I've worked extensively with the STC chips and while they are decent, reliable and cheap, there is zero library support compared to Arduino. STC provides demo code for using the timers, serial, PWM and ADC subsections, it's up to you to make what you need which means you will be writing almost everything you need, from scratch.
If you're fluent in Mandarin Chinese, there is considerably more support and code sharing since the product is sponsored by the Chinese government. Outside of the domestic Chinese market there is zero, zip, nada support.
There are tons of STC "development boards" on Aliexpress. Find one with the same series part you have (12C) and start there. You'll need a logic analyzer to figure out what display driver you have. Realistically, you need at least one more original "flasher" board for testing and experimentation. I guarantee you the journey will be long. If you're someone who gives up easily, don't start.