On my previous laptop (Acer Travelmate) I had a dedicated key for Euro sign. My current laptop doesn’t have this button, that’s why let me share the way you can input it from your keyboard. This method is suitable for any OS.
In order to add € sign, please, do the following:
Hold Alt button and input 0128. Release Alt button to see the Euro sign.
0128 is the ASCII code for Euro. If you know any other ASCII code values, you can input them directly using Alt shortcuts.