READ OUT LOUD. Choose which marked text you prefer to practice with - macrons or accent marks - and read the text out loud until you feel comfortable and confident. Then, try reading the unmarked text at the bottom. It should be easy for you after practicing with the marked texts. :-)
MACRONS. Here is the text with macrons:
Rūmor erat parturīre Montēs. Hominēs undique accurrunt et circumstant, mōnstrī quidpiam nōn sine pavōre expectantēs. Montēs tandem parturiunt; exit rīdiculus Mūs.
ACCENT MARKS. Here is the text with ecclesiastical accents, plus some color-coding for the words of three or more syllables (blue: penultimate stress; red: antepenultimate stress):
Rumor erat parturíre Montes. Hómines úndique accúrrunt et circúmstant, monstri quídpiam non sine pavóre expectántes. Montes tandem partúriunt; exit ridículus Mus.
UNMARKED TEXT. Here is the unmarked text - after practicing with the marked text that you prefer, you should not have any trouble with the unmarked text:
Rumor erat parturire Montes. Homines undique accurrunt et circumstant, monstri quidpiam non sine pavore expectantes. Montes tandem parturiunt; exit ridiculus Mus.
IMAGE. Here is an illustration for the story (image source).