I have added the Tab to the Navigation Menu through Mobile Navigation.
But I am not able to see my whole page on my mobile screen, not even scroll bar is available. Is their any change in CSS so that whole page will get displayed.
You'll need to define a Compact Page Layout for each page in your App. If you don't, you'll get the default Compact Page Layout. See the Salesforce1 Mobile App Admin Guide for more on this. If you're using Flex Pages, you'll also want to look at the Salesforce1 Mobile App Developer Guide.
Generally speaking, only what you define on a Compact Page Layout will appear in the view in a Mobile App. Even then, at most, only the first 4 items will appear when you go to that item until you ask for more. The Default Compact Page Layout typically only provides for 3 items to appear on a page. Again, I refer you to the documentation to learn more.