Searching for a book

Hello, I just started using Calibre and .. I must be not very bright, but ..
How do I search for a book whose title I know only approximately?
So, let's say, I know part of the title. And I do not know if this part is the start, end or middle of the complete title. I want to get all books "where tittle like '%Something%' ? How do I do this?

Same goes for author...

Also, is there a way to change the theme to a light one?