Hi Sudhakar,
You should review the frdm-k64f schematics. UART4_RX/TX go to the J199 pins 3 and 4 respectively.
Please note that there is no UART PHY so you would need to add one or jumper these connections to a TWR-SER card.
In the future please add more information about the tool chain you are using and what software you are using. If it is a project you create or modify posting it helps you to get support faster.
Another source for getting help is to search the Community for previous posts.
Here is one to review that has code example to access UART4 in a loopback mode (i.e. jumpered TX to RX).
Cannot debug generated fsl_uart code that is freezing in SendDataBlocking function
Regards,
David