Learn Portuguese (Portugal): Leste o artigo naquela página do jornal? - Did you read the article on that page of the newspaper?

The verb form leste already tells us exactly who did the reading. The -ste ending is only ever used for tu (informal you) in the past tense. You could say Tu leste, but native speakers usually drop the pronoun unless they want to add special emphasis.

"Leste" looks very different from "ler". Is this a regular past tense ending?

No, ler (to read) is irregular in the past tense (Pretérito Perfeito). Instead of a standard ending, the tu (informal "you") form becomes leste. For comparison, the eu (I) form is li and the ele/ela/você (he/she/you formal) form is leu.

Where does the "n" in naquela come from?

It comes from the preposition em, which means "in" or "on". In Portuguese, things are often said to be "in" a page rather than "on" it. When em combines with aquela (that), they merge into the single word naquela (on that).

Why do we use do jornal instead of just de jornal?