You cannot import an XLSX file into MongoDB directly. However, what you can do with an Excel spreadsheet is save it as a CSV file, then use mongoimport to import it into MongoDB. You can find the documentation for mongoimport here, but in any case, the command you need to run should look something like the following:
mongoimport --db myDb --collection myCollection --type csv --headerline --file /path/to/myfile.csv
In the command above, the --headerline flag indicates that the first line in your file contains the name of the fields. There are many other options you can use depending on your needs. These are highlighted in the documentation.