Most modern Ashkenazi siddurim indicate stress using a meteg, which is a small vertical line placed under the letter that begins the accented syllable. For example, the word v'tsivanu (from many blessings) is accented v'tsiVAnu, and that's indicated by וְצִוָּֽנוּ. When the meteg isn't present, the accent is on the last syllable. Such is the case for siddurim from Artscroll and Koren, the Authorised Daily Prayer Book (from England), the Sim Shalom siddur (at least the edition I see in images online), and Mishkan T'filah. Surely many others follow suit.
Another system is used by the siddur Rinat Yisrael: when they want to emphasise the accent, they place a mahpach over an accented syllable when it's not the last syllable, and a zarqa over the final syllable when the accent is on the last syllable. Their introduction implies that unmarked might have accent anywhere, and you just have to know.
For the chumash, the cantillation marks will almost always tell you the syllable to accent. The exceptions are telisha gedola (which is always written before the word), and telisha ketana, pashta, zarqa, and segol (which are always written after the word). In most modern chumashim (for example, the Artscroll one you have), these signs are repeated over the syllable they want you to accent (although note that these are editorial decisions — the earliest texts we have don't double these signs, so there are a few cases of disagreements as to the accented syllable). Additionally, the y'tiv appears only before the word, but since it only appears on a word that is accented on its first syllable, you can essentially ignore this exception. There are more subtleties, like secondary accents, but these rules will hold you in good stead all of Tanakh except for Job, Psalms, and Proverbs, which (mostly) have their own system of cantillation. See more on this here and here.