This doesn’t depend on iTalkie. It’s completely a question of the standard way to input those characters on your device. If you’re using a computer, then there will be standard key combinations for special characters. If you’re on iOS, holding down a letter key pops up accent options. Android might be similar but I don’t use it so I can’t say.

Maybe you need to download the Spanish keyboard. Or copy and paste the symbols from Google if you look for the alphabet and punctuation marks in Spain :)