How to write en and em dashes?

I understand that to be able to type en and em dashes I have to configure the COMPOSE key, or something like that, but I am not sure about that nor on how I get from there to be able to type en and em dashes in addition to the minus sign.

How do I type en and em dashes on Ubuntu GNOME 15.10 with GNOME 3.18?

I have now looked at this answer, so I would now also like to know the code for the en dash and how to assign other keyboard shortcuts to these Unicode characters, as I don't want to have to type something too long in order to get these.

You need to learn the Unicode numbers of these two characters. They are not actually hard to remember, because they look like years. ;)

• En dash: U+2013
• Em dash: U+2014

To write a Unicode symbol, perform the following actions:

• Press Ctrl+Shift+U (the display will show something like u̲)
• Type the code (e.g. 2014)
• Press Enter

There you go: – —

For a complete reference to Unicode characters, run gucharmap.

When I look up "em dash" on the gnome 3 overview a result comes up that puts it on the clipboard. I think you need to have gnome-characters installed for it to work.