READ OUT LOUD. Choose which marked text you prefer to practice with - macrons in verse form, or macrons in prose order, or accent marks in prose order, or focusing on the meter. You will find materials for all of these options below. :-)
VERSE MACRONS. Here is the verse text with macrons:
Iam Mustēla suīs languēns et tardior annīs,

Ergō quaerendī praedās excogitat artem,

Frūmentī furtim sēsē implicat illa maniplō,

Hūc frūgēs quoniam veniunt arrōdere Mūrēs,

Cum tē dēficiunt imbellī corpore vīrēs,

PROSE MACRONS. Here is the same text with macrons written out in prose word order:
Mustēla iam languēns annīs suīs et tardior, nōn potis erat, ut mūrēs assequerētur. Ergō artem praedās quaerendī excogitat, hāc arte ūtēns mūribus īnsidiāta fuit. Illa furtim frūmentī maniplō sēsē implicat, hāc fraude latet, cibōs parāre cōnāta. Quoniam Mūrēs hūc veniunt frūgēs arrōdere, incautōs capit, labōre paene nullō. Cum vīrēs tē dēficiunt, imbellī corpore, prūdēns, cōnsiliō ūtere; cēdet opus.
STRESS (ACCENT) MARKS. Here is the prose text with accents, plus some color-coding for the words of three or more syllables (blue: penultimate stress; red: antepenultimate stress):
Mustéla iam languens annis suis et tárdior, non potis erat, ut mures assequerétur. Ergo artem praedas quaeréndi excógitat, hac arte utens múribus insidiáta fuit. Illa furtim fruménti mániplo sese ímplicat, hac fraude latet, cibos paráre conáta. Quóniam Mures huc véniunt fruges arródere, incaútos capit, labóre paene nullo. Cum vires te defíciunt, imbélli córpore, prudens, consílio útere; cedet opus.
ELEGIAC COUPLET METER. Below I have used an interpunct dot · to indicate the metrical elements in each line, and a double line || to indicate the hemistichs of the pentameter line.
Iam Mus·tēla su·īs lan·guēns et· tardior· annīs,

Ergō· quaeren·dī prae·dās ex·cogitat ·artem,

Frūmen·tī fur·tim sē·s~ implicat· illa ma·niplō,

Hūc frū·gēs quoni·am veni·unt ar·rōdere· Mūrēs,

Cum tē ·dēfici·unt im·bellī ·corpore ·vīrēs,

IMAGE. Here is an illustration for the story from the 1574 edition of Osius:
What follows is an unmarked version of the prose rendering to faciliate word searches: Mustela iam languens annis suis et tardior, non potis erat, ut mures assequeretur. Ergo artem praedas quaerendi excogitat, hac arte utens muribus insidiata fuit. Illa furtim frumenti maniplo sese implicat, hac fraude latet, cibos parare conata. Quoniam Mures huc veniunt fruges arrodere, incautos capit, labore paene nullo. Cum vires te deficiunt, imbelli corpore, prudens, consilio utere; cedet opus.