Learn Italian: Lo devono riparare oggi. - They must repair it today.

When you have a modal verb like devono (they must) followed by an infinitive verb like riparare (to repair), you have two choices for where to put an object pronoun like lo. You can put it before the conjugated verb, as seen here (Lo devono riparare), or you can attach it to the end of the infinitive. Both are completely correct and mean the exact same thing.

How would this sentence look if I attached lo to the end instead?

It would be Devono ripararlo oggi. To attach a pronoun to an infinitive verb, you drop the final -e of the infinitive. So, riparare becomes riparar-, and then you add lo to make ripararlo.

How do we know lo means "it" and not "him"?

Without more context, we do not know for sure! Lo is a direct object pronoun that replaces any masculine singular noun. It could refer to a broken computer (il computer), which translates to "it", or it could refer to a person and mean "him". We translate it as "it" here because objects are repaired more often than people, but grammatically it can be either.

Why is the word loro ("they") missing from this sentence?