I recently start work with FreeRTOS on kintex-7 and can’t understand how to show something on display, and what library I should use.
FreeRTOS itself, doesn’t come with drivers for these sorts of devices. Generally you need to look at the manufacturer of the device to find out what you need to do to talk to it, and they may have libraries that can be adapted for use (if you are really lucky, they may even directly support FreeRTOS or define an RTOS adaptor layer).
You will also need to know (or figure out) how the device has been (or needs to be) connected to your CPU chip.