You can't always translate word for word.
"are" here has no separate meaning; it's just a helping verb used to form the present continuous tense "are reading" of the verb "read".
In Esperanto, this is often expressed simply with the present tense legas, which doesn't need a helping verb.
If you explicitly want to point out the on-going nature of the activity, you could use the progressive: la virinoj estas legantaj. That form does use a helping verb, which happens to be esti (to be) as well.
But unlike in English, the explicit progressive forms are not required for on-going actions.
There was a glitch. The system asked me to type: Ili estas belaj leteroj. It marked that correct, then it asked me to type the same thing again: Ili estas belaj leteroj. It marked that wrong and reported that I was supposed to have typed: La virinoj legas la ĵurnalon.
So there was a glitch in the DuoLingo Matrix, and I've written about it here in the hope that some administrative person will check it out.
I was doing the "accusative" workshop.
The very next spoken thing I was asked to type was: La virinoj legas la ĵurnalon. That was marked wrong and the system informed me that I should have typed: Mi manĝas pomon.
I see the pattern. The spoken phrases are one list-item behind the typed phrases. I'm going to log out and log back in to see whether that fixes the glitch.