Use iCloud.com

You can access your iCloud information using a computer web browser instead of using apps on your iOS device, Mac or Windows computer. You go to iCloud.com, sign in, and then use the iCloud.com web apps: Mail, Contacts, Calendar, Notes, Reminders, Find My iPhone, Pages, Numbers and Keynote.

To prevent anyone from accessing your iCloud information on iCloud.com (such as your email) while you’re away from your computer, you can sign out. If you’re now signed in from more than one browser, you can sign out from all browsers at once.

Sign in to iCloud.com

Go to Apple ID (the one you use with iCloud).
If you select “Remember me,” then anytime you return to iCloud.com within two weeks you are not asked to sign in (except to use Find My iPhone, which continues to require your password). You stay signed in to iCloud.com even if you refresh your browser window, close the browser window where you are logged into iCloud or quit the web browser.

For troubleshooting tips, see If you can’t sign in to iCloud.com.

Sign out of iCloud.com

To sign out from the browser you’re using now, click your account name at the top of the iCloud.com window, then choose Sign Out.
If you didn’t select “Remember me” when you signed in to iCloud.com, you can also sign out by quitting your browser app.
Note: You can sign in to iCloud.com from more than one browser at a time. Signing out of iCloud.com from one browser does not sign you out from other browsers.
To sign out from every browser where you’re now signed in, click your account name at the top of the iCloud window, choose Account Settings, click Advanced, then click Sign Out of All Browsers.