I need more flash and SRAM for my LPC 1768 project. Can I add 4M flash and 4M SRAM for LPC 1768? If yes, can I run the code in external flash same as internal flash and use external SRAM in the same way as internal SRAM?
These are questions about the NXP LPC1768 chip - not about Keil tools.
Your first step has to be to study the documentation (Datasheet & User Manual) that NXP provide for their chip...
Just look in the user manual - does it even have an EMC...?
What is the main difference between LPC1768 and LPC1778?
If you read about the EMC in the user manual for 177x and 178x - do you notice how they mention the signals available for 144-pin, 180-pin and 208-pin chips? How many pins have your 1768?
What did the EMC chapter say for 1768? You did find such a chapter?