If you have downloaded a keyboard onto your Mac but it doesn't seem to be working as you expected, it may be that you have not fully installed it. Installing a keyboard on a Mac is a little more complex than installing a keyboard on a Windows machine.

Once you have downloaded the keyboard, find the keyboard file in your downloads folder and open it. This will open up a new window called ‘Keyboard’ with two files in it. Select the one with the extension .keylayout.

Next, open up a new Finder window, go to your ‘Library’, and select ‘Keyboard Layouts’. Drag the .keylayout file over into your ‘Keyboard Layouts’.

Then, under the Apple menu, go into ‘System Preferences’ and select ‘Language and Text’ (this is called ‘International’ in some versions of the Mac OS). Click on ‘Input Sources’ (sometimes called ‘Input Menu’), scroll through the list of keyboards, and put a check mark next to the keyboard you have just downloaded.

Finally, you need to select the keyboard from the keyboard menu. This usually appears as a small icon of a flag or a little box containing the letters ‘U+’ in the top right-hand corner of your screen. Click on this to see a list of key layouts on your machine, and select the one you need.

Once a keyboard has been successfuly installed on your machine, you need only to select it from this keyboard menu each time you need it; you don't have to go through the whole process every time. In the same way, once you are finished using your new keyboard and wish to switch back to a different one, use the keyboard menu to do this also.