Learn French: L'ordinateur est en panne. Je ne l'ai pas utilisé. - The computer is broken. I did not use it.

In the passé composé (past tense), ne and pas act like a sandwich around the helper verb, which is ai (have) in this sentence. The past participle (the main action word, utilisé) comes after pas.

What does the l' in Je ne l'ai pas mean, and why is it placed there?

The l' is the pronoun "it", taking the place of the masculine noun l'ordinateur (the computer). In French, object pronouns are placed immediately before the conjugated helper verb (ai). Because the word le followed by ai creates a vowel clash, it shortens to l'ai.

Why is the order Je ne l'ai pas instead of putting ne right next to the verb ai?

When you use an object pronoun like l' ("it"), it sticks tightly to the front of the helper verb. The negative words ne and pas must go around that entire glued-together chunk. So, the order to remember is always: ne + pronoun + helper verb + pas.

Why does en panne translate to "broken"?