To set up iCloud on your compatible iOS or OS X device, go to iCloud.com, enter your Apple ID and password, and click the Sign In button. To create a new account, click the Create One Now link and follow the prompts.
When setting up an account for iCloud, you need to have access to at least one Apple device and the Internet. Type iCloud.com in your Web browser and provide your first and last name, your date of birth, a password and three security questions. Create a password that contains upper and lower case letters with at least one number and eight characters. After completing all mandatory fields, click the Continue button.
If you have an existing iCloud account, use your current login credentials to set up iCloud on your device. On a Mac computer, turn on iCloud by opening System Preferences from the Apple menu on your dock. Click on the iCloud icon located in the middle left section of the window and select each iCloud service you wish to activate. If you are using an iPhone, iPod touch or iPad, tap the Settings app, then tap iCloud and log in with your iCloud credentials.
Apple debuted the iCloud service in October 2011. As of 2015, iCloud provides cloud storage for over 300 million Apple customers.