Almost certainly the easiest thing to do is to connect the TxD1 or TxD2 to the RX pin of the 16F877A. Obviously connect the ground pins of the RCB-4H to the grounds of the PIC16F877A.
If you set up the USART on the 16F877A with the right baud rate (9600 for TxD1 or 57600 for TxD2, I think), you should be able to receive the data strings.
You obviously need to have a programme that parses the data strings. **broken link removed** gives an idea of how the parsing should be done.