How can I overlap notes on a measure?

Oftentimes on scores I see a staff with what looks like two different lines of notes, and notes will play on top of each other (pictured below). For instance, in a 2/4ths time signature there will be a half note that takes up the whole measure and another note on that same measure. However I cannot figure out how to do this when arranging scores. How can I do this when making scores?