To type Spanish letters, you will need to hold down the "Alt" key 
found next to the space bar and the following numbers:
á (Alt - 160)
é (Alt - 130)
í (Alt - 161)
ó (Alt - 162)
ú (Alt - 163)
ñ (Alt - 164)
¿ (Alt - 168)
¡ (Alt - 173)

(Note:  Make sure that the "Number Lock" key is on and that you are 
using the numbers to the right of the keyboard.)