Go to the CONFIG setting and choose SIGNAL SOURCE > SELECT > EXT, and choose EXT SELECT > J1.
Next, apply 0 to ±10 V between the pin No. 23 and 24 of the J1 connector.
For the details, read the user’s manual – chapter of External Control, Parallel Operation, and Synchronization – Controlling DC Signals – Using External Voltage.
Please note that while the J1 connector can be used to control the DC output, if you want to control the AC output or perform high-speed control, it is recommended that you use the EXT SIG IN terminal on the panel instead, as it enables faster operation and allows you to set the gain setting.