Question about accent marks
I notice that Duolingo has accent marks on their words. Is that to help us know what words should be accented? Looking through some Russian text that I have from elsewhere, I don't see any accent marks.
It is common to have accents in books for small children and textbooks for foreign learners. Because otherwise... imagine an English textbook without any transcription. Memorising hundreds and thousands of words with the pronunciation you think is right is a practice sure to backfire later.
Since Duolingo was not very enthusiastic about doing any programming for accent marks, we only have them in tips and in picture exercises.
Actually, there are accent marks in regular texts to avoid ambiguity. Search for an accented word "бо́льшая" in these links (it is a word from regular text that uses the accent mark the most):
as others have pointed out, the accents are just a help to learn which syllables are stressed. This is especially important in russian because the pronunciation of some of the vowels change depending on whether they are stressed or not (e.g. o is pronounced o when stressed but more like a when not stressed)