Issue in CP2102 Breakout module interface with PIC16F877a microcontroller
Depending on the protocol you can get away with just TXO, RXI, and ground for sending data both ways. DTR and CTS are hardware handshaking lines that your PIC program would have to control and read using additional I/O pins beyond the dedicated PIC UART pins.

TXO is an output and goes to the PIC RX input, RXI is an input and goes to the TX output on the PIC.

If you are not powering the PIC from the USB you should add some series resistors on the data lines (everything but ground and Vcc), something like 1K, to deal with one side being powered and the other not.