Yes, you can!

You'll need to put your number list into CSV format.

Excel Spreadsheet:

If your list is currently an excel spreadsheet, you can convert it by clicking File > Save As, then changing the type to "Comma separated values (CSV)"

Plain text list or other formats:

If your list is in word, or another format, you will need to copy and paste the numbers into a plain text file. 

The text file should consist of one fax number per line.