Make sure that you have the correct fonts loaded into your system fonts directory. Do a search on this forum as to how exactly Boris handles fonts, there have been many posts in the past.
Now, make sure that your keyboard is set to spanish. If your accents are not showing up, check that they are showing up in other applications, such as word.
If you absolutely can't get the accents to show up, then use the charmap app that comes with windows (I am assuming you are on windows) to copy and paste the accents to your text. This app can be accessed by going to start - run - type charmap into the run dialog box.
I use french accents inside Boris Red all day at work and have issues. When I need non-french accents I use charmap to get them in.