Common question that is asked repeatedly. Short answer. Officially you cannot access the Dashboard from a remote computer.
Unofficially one can but it requires one to either use VPN or to use SSH and possibly modify the firmware to allow for remote Dashboard Access.
Here are just a few past threads to get you started:
https://community.wd.com/t/login-to-mycloud-dashboard-from-outside-the-network/93201
https://community.wd.com/t/how-to-access-dashboard-remotly-throgh-browser/147803
https://community.wd.com/t/access-dashboard-remotly-via-internet/94902
https://community.wd.com/t/configuring-remote-dashboard-access-can-it-be-done/92873
