how do i show the keyboard character map

System Preferences > Keyboard > check Show Keyboard & Character Viewers in the menu bar this will give you an icon in your menu bar that will give you quick access to the character map

It should look like this:

You're welcome

martinishome wrote:

I want to use an octothorpe but its not a standard key

What kind of keyboard are you using? It's printed on shift 3 in the normal US one: #