For use TFTGLCD Adapter you need
1. Replace files in Marlin-bugfix-2.0.x\Marlin directory with new from this directiry excluding Configuration.h - it for example only.
2. Comment line with current selected panel in yours Configuration.h file and place new line with "#define TFTGLCD_ADAPTER" insted.
3. You need check section with "#elif ENABLED(TFTGLCD_ADAPTER)" in src\inc\Conditionals_LCD.h for right parameters for panel.
4. If you are planning connect TFTGLCD Adapter by SPI bus you need add some new lines to file "pins_YOURS_BOARD_NAME.h".
Simplest way to do this - change section with "#if HAS_SPI_LCD". For examle, old section:

#if HAS_SPI_LCD
  #define BEEPER_PIN       P1_30   // (37) not 5V tolerant
  #define BTN_ENC          P0_28   // (58) open-drain

  #if ENABLED(CR10_STOCKDISPLAY)
    #define LCD_PINS_RS    P1_22

    #define BTN_EN1        P1_18
    #define BTN_EN2        P1_20
.......
.......
#endif // HAS_SPI_LCD


new section:

#if ENABLED(TFTGLCD_ADAPTER)
      #define BEEPER_PIN      -1    //disable board beeper
      #define BTN_ENC         -1    //disable board encoder
      #define BTN_EN1         -1
      #define BTN_EN2         -1
      #define DOGLCD_CS       P3_26 //on EXPn connector with SPI bus
#else
#if HAS_SPI_LCD
  #define BEEPER_PIN       P1_30   // (37) not 5V tolerant
  #define BTN_ENC          P0_28   // (58) open-drain

  #if ENABLED(CR10_STOCKDISPLAY)
    #define LCD_PINS_RS    P1_22

    #define BTN_EN1        P1_18
    #define BTN_EN2        P1_20
.......
.......
#endif // HAS_SPI_LCD

#endif	//TFTGLCD_ADAPTER

You may find examples for 3 boards in "pins" directory.

You may use disabled beeper and encoder pins for other tasks.