In English, we can say I had used or I had worked when we're talking about something we don't do anymore. You can do basically the same thing in Italian!
First, use the past form of avere that matches who you're talking about.
| subject | verb (avere) |
|---|---|
| io I |
avevo had |
| tu you |
avevi had |
| lui / lei he / she |
aveva had |
| noi we |
avevamo had |
| voi you all |
avevate had |
| loro they |
avevano had |
Then you'll change the next verb ending to ‑ato, ‑uto, or ‑ito.
The past of avere plus a verb is used to say things like io avevo parlato, which means I had spoken.
But some verbs that talk about motion (like venire and andare) use essere instead of avere.
Verbs that include extra little words, like mi ero ricordato, also use essere in these cases.
Remember that verbs that use the past of essere have different endings depending on who is doing what. The endings change depending on gender...
... and they also change depending on whether you're talking about one person or multiple people.