In the settings for your keyboard there is a setting for the US international keyboard. If you choses that you can toggle between the regular keyboard and the international keyboard using the keyboard icon in e lower left of the menu bar across the bottom. Then you just type 'a which will appear as á or ~n for ñ. Otherwise you have to learn the ASCII codes which is a drag. My iPad is easier than either.

In Windows 7, for example, you can go to Start menu Help and search for "Change your keyboard layout" then follow the easy instructions to set your keyboard to Spanish. You can then toggle back and forth using the icon in the tool bar, however, it's fine to use the Spanish keyboard to type English. You'll need to google "Spanish keyboard" to see what the layout is, but I believe you'll find it's really easy to use, and has additional accents for writing French and Catalán as well. The diaerisis also works as an Umlaut, if you're into German.

Control Panel => Clock, Language, and Region => Change Keyboard or other input method => Change keyboards => general