One day at church our daughter was wearing some new shoes. Since anything that clean on a toddler would have to be new, someone asked if she was estrenando her new shoes.
We had never heard this word before, so they explained when you use or wear something for the first time it is estrenar. In English we would say debut.
‘Estreno de una pelÃcula’ is another use for this, the first day a movie is showed in the cinema