This is the 159th most frequent Italian word.
mettere
"Mettere" means "to put" or "to place."
In this sentence, 'mettere' is used in the sense of placing or positioning something somewhere.
Devi mettere il libro sul tavolo.
You need to put the book on the table.
Here, 'mettere' is employed figuratively to express the idea of applying or dedicating effort.
Dovresti mettere più impegno nei tuoi studi.
You should put more effort into your studies.
In this usage, 'mettere' conveys the action of setting or proposing something (in this case, for sale).