Learn Spanish (Latin America): Lo estamos revisando ahora.

In Spanish, direct object pronouns like lo (it) usually go right before the conjugated verb. Here, estamos is the conjugated verb, so lo is placed just before it.

Can I put lo somewhere else in this sentence?

Yes! When you use the present progressive (an ongoing action using estar), you can attach the pronoun directly to the end of the action verb. You could also say Estamos revisándolo ahora. Notice that attaching it to the end requires adding an accent mark to keep the spoken stress on the correct syllable.

How do I know revisando means "checking" and not just "check"?

The -ando ending is the Spanish equivalent of the English "-ing" for verbs that originally end in -ar (like revisar, meaning "to check" or "to review"). When combined with estamos (we are), it creates the ongoing action "we are checking".

If I wanted to say "We are checking nothing right now", how would I change this sentence?

You would drop lo and use the negative word nada (nothing). In Spanish, when a negative word comes after the verb, you must also put no before the verb. So it becomes: No estamos revisando nada ahora.