following the instructions in the manual for the AT-ETU-SYNC may get you close but we have been finding windows is not using the correct Driver for talking to the AT-ETU-SYNC.
https://atlona.com/pdf/manuals/AT-ETU-SYNC.pdf
Download the MaxLinear Driver and extract. Go to Device Manager, right click on the USB Device, select Check for Updates. Then point this to the folder with the MaxLiner Driver in it where it was saved.
Then you will be able to connect to the AT-ETU-SYNC as in the manual
Launch the desired client. Atlona recommends the Hercules client, available here: https://www.hw-group.com/software/hercules-setup-utility
Configure the following RS-232 settings in the client:
Baud rate: 115200
Data bits: 8
Parity: NONE
Flow control: None