Why can't I access iCloud from my iPhone or iPad

Why can't I access iCloud from my iPhone or IPad? When I try I do don't get the log in landing page but instead only the options to set up the device (both a lady are), to install find my phone or install find my friends. I just want to move some contacts into groups that have already been set up. Why is apple making it so difficult to manage your contacts? Its bad enough that you can't create the groups from the Address Book app that comes with the device--you can only do it from iCloud. Now I can only get to iCloud from my desktop? Am I missing something?