Copy the "Nextion_HMI" folder in to your project, then include to your project the "Inc" folder.
Steps are:
Right click on to your project Name, then choose Properties
Click on to "C/C++ Build - Settings"
Click on Add under ToolSettings/MCU GCC Compiler/IncludePaths
Click on Workspace and choose the "Nextion_HMI/Inc" folder
Click on Apply
Click on MCU Settings, Use float with printf
Click on Apply and Close
This is my chosen clock settings, configure according your needs.
Choose the UART you want to use.
Mode: Asynchronous.
Parameters: 9600, 8 N 1
Enable Global Interrupt for chosen UART
Tick mark Generate IRQ Handler for chosen UART
Choose an a unused timer for Timebase Source. (FreeRTOS will use SysTick timer)
Enable FreeRTOS, choose CMSIS_V2 and create tasks