Set your keyboard to United States-International.
Then entering Spanish characters will be fairly easy. For instance, if you want accentuation on vowels, just type the apostrophe key (you won't see anything at first) followed by the vowel. The tilde above the n can be obtained by using Ctrl+Alt then the letter n (ñ). Inverted ?, same thing: Ctrl+Alt then the question mark key (¿), this could also be done with the inverted exclamation mark; just use the appropriate key (¡). What else? Of the dieresis, (I think that's what they're called), in words like pingüino, ungüento can be obtained by Ctrl+Alt then the letter y.
Others: «» = Ctrl+Alt then [ or ] respectively. Actually everything I just learned everything can be obtained using the Ctrl+Alt combination, including accentuation:
á = Ctrl+Alt then letter a ... etc é, í, ó, ú. I just prefer typing the apostrophe key first then the letter (faster)
If you want accented letters to be capitalized? Either:
Ctrl+Alt+Shift then the letter (Álvaro) or hit the apostrophe key first then Shift+letter: É.
PS: The ü can also be obtained by keying the double-quotation mark key (Shift+'), then the letter: ü,ï.
¡Ojalá que te ayude!