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:
Rēpserat in fabricam serpēns, līmāque repertā,

Rīsit līma; rogat serpēns cūr rīserit, inquit:

Ipsum perdūrum mōs est mihi rōdere ferrum,

Tū mē rōdentem, stultissima, rōdere tentas:

Mordācem prohibet mordērī fābula nostra,

Hinc discant hominēs nē laedant sē potiōrēs,

PROSE MACRONS. Here is the same text with macrons written out in prose word order:
Serpēns rēpserat in fabricam, et, līmā repertā, escam esse putāns, eam rōdere coepit. Lima risit; serpēns rogat cūr rīserit; inquit: Iure rīdeo, stultitiam tuam mirans. Mihi est mos ferrum ipsum perdūrum rōdere, et sī quid ferrō dūrius esse potest. Tū, mē, rōdentem, rōdere tentas, stultissima: aspice! iam sanguine rubeō tuō tincta. Fabula nostra mordācem mordērī prohibet , nē et ille laesus vicem nimiam reddat. Hinc hominēs discant nē laedant sē potiōrēs, nē, dum laedere cupiunt, mage laedantur!
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):
Serpens répserat in fábricam, et, lima repérta, escam esse putans, eam ródere coepit. Lima risit; serpens rogat cur ríserit; inquit: Iure rídeo, stultítiam tuam mirans. Mihi est mos ferrum ipsum perdúrum ródere, et si quid ferro dúrius esse potest. Tu, me, rodéntem, ródere tentas, stultíssima: áspice! iam sánguine rúbeo tuo tincta. Fábula nostra mordácem mordéri próhibet , ne et ille laesus vicem nímiam reddat. Hinc hómines discant ne laedant se potióres, ne, dum laédere cúpiunt, mage laedántur!
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.
Rēpserat· in fabri·cam ser·pēns, lī·māque re·pertā,

Rīsit· līma; ro·gat ser·pēns cūr· rīserit,· inquit:

Ipsum· perdū·rum mōs· est mihi· rōdere· ferrum,

Tū mē· rōden·tem, stul·tissima,· rōdere· tentas:

Mordā·cem prohi·bet mor·dērī· fābula· nostra,

Hinc dis·cant homi·nēs nē· laedant· sē poti·ōrēs,

IMAGE. Here's an illustration for the fable (image source) from a Renaissance edition of Aesop:

What follows is an unmarked version of the prose rendering to faciliate word searches:
Serpens repserat in fabricam, et, lima reperta, escam esse putans, eam rodere coepit. Lima risit; serpens rogat cur riserit; inquit: Iure rideo, stultitiam tuam mirans. Mihi est mos ferrum ipsum perdurum rodere, et si quid ferro durius esse potest. Tu, me, rodentem, rodere tentas, stultissima: aspice! iam sanguine rubeo tuo tincta. Fabula nostra mordacem morderi prohibet , ne et ille laesus vicem nimiam reddat. Hinc homines discant ne laedant se potiores, ne, dum laedere cupiunt, mage laedantur!