First made a serial cable, attention Vax use a DEC423 serial port designed for long distant terminal line:

--------------- 1 - DTR (Data terminal ready)
I             I 2 - TxD (Transmit data)
I    1  2  3  4  5  6   I 3 - GND (Signal ground)
I                                         I 4 - RxC (Receive common)
I                                         I 5 - RxD (Receive data)
---------I____I 6 - DSR (Data set ready)

Pin 2 of the phone connector goes to Rx pin of the serial (3 of DB25 or 2 of DB9), pins 3 & 4 go to ground (7 of DB25 or 5 of DB9), and pin 5 goes to Tx pin (2 of DB25 or 3 of DB9).

Then, make sure that the S3 switch (on the front of the 4000/60) is set to the up position so that the VAX uses the serial console instead of the graphics console.

Then, load up your favourite terminal application, set the speed to 9600 baud, make sure hardware handshaking is off, and see if you can talk to the VAX.