Really quick: there are a couple of ways to access the admin dashboard for the My Cloud device:
1.Enter the Device Name that is listed in the dashboard settings into the address bar.

So, in my case, I’d enter http://PAUL-NAS (http://PAUL-NAS.local for OSX) into my browser address bar. This will bring me to the dashboard login. Enter your Device username and password you set during the initial setup.
Note: the Device Name is set to “WDMyCloud” by default. If you want to rename it try doing so during the initial setup since changing names later may cause issues.
2.Enter the device IP into the address bar.
During the initial setup, you’ll see an IP in the address already in the bar. However, since the device is defaulted to DHCP, the IP will more than likely change. So, if you see 192.168.1.5 now, it may not work next time since the router assigned the device a different IP.
Go to Settings > Network > Network Services > set to Static from DHCP
Set the IP address and verify the Subnet Mask, Gateway, and DNS — (cmd > ipconfig /all). I set mine to .100 (last octet). You can also try doing this via Address Reservation settings in your router.
In the end, accessing the admin dashboard using either approach is the same. It’s just that option 2 takes a little more configuration. But, you’ll always know what your My Cloud ip address is.