If there isn’t a written accent, then there is a pattern to which syllable gets stressed. In words that end with a vowel or the consonant -n or -s, the stress is on the second to last syllable. With any other consonant, the stress is on the last syllable. Any stress that breaks that rule requires a written accent. Written accents are only found on vowels (á, é, í, ó, ú) and there can only be one of them per word.
The ñ is technically an accent but doesn’t count in the “one per word” thing, it means you pronounce the letter like “ny” (or like the “gn” in lasagna).
There are a few other accents things (like when do you hear the “u” after a “g”, certainly not in the word guitar but yes in the word penguin: guitarra, pingüino) but I won’t get into that now, we probably won’t meet too many penguins on Camino.