I am need to use Assamese Inscript (unicode font) in ubuntu desktop for data entry process but I found only Bengali not Assamese.
First, undo the keyboard layout method if you still have it, if you don't you will have two keyboard icons on the top panel and that will confuse you. Return to keyboard layout and remove Hindi and any other layouts you have added except the default English. This will remove the keyboard icon from the top panel.
Second, Using Ubuntu Software Center install ibus-m17n. The m17n module will give you more Indian keyboard layout choices.
See How do I enable writing in Indian languages? for more details.