A primary stress is the strongest accent in one word, or breath group, and for your word in particular, accommodation, əkɒməˈdeɪʃ(ə)n, the primary stress would be in the second part of the word, like I marked. There is a secondary stress, after the first sound, meaning, əˌkɑməˈdeɪʃ(ə)n, that would be both the primary and secondary quest!
Hope this helps!