You cannot login to iCloud.com as apple believes all the features you require to use iCloud are already built in to the iPad / iPhone. Like the contacts app calendar app etc.
I'm fact the only thing I'm aware of that you need to login in to iCloud.com for is to reset your photo stream , you can't do that directly on the iPad.
The IPad Forum is a community of members from all walks of life and from all over the world coming together to share our experiences and to help each other learn about this wonderful piece of technology the Ipad. There is a wealth of information already here in the many threads we have so doing some searches will answer most of the questions you have. If then you cannot find the answer you are seeking then by all means post your question. There are many friendly and informed members here only too willing to help you.