You did not say what system you have but the following is for Windows 7.
If you want to sign in by wd2go.com then you should see the following, see image below. Provide the information and then click sign in.
If you are looking for your My Cloud on your computer then click Start►All Programs►Western Digital►WDMyCloud and open up your My Cloud. Under the icons you will see your address, example 196.198.1.222. You can click on the icons and open up your My Cloud. See image below. If you are wanting to open your Dashboard then use the address under the icons, example http://196.198.1.222, to open it.