I'm not sure why all fields are in one column. Here's a couple of options:

1/ If you have access to the admin area, go to "Global Setting" > "Data Import Tools" > "Product Import"

At the top of that page you will see an option to down a new file/template: "click to download the Sample File (used as a reference for uploading)."

Alternatively: 

2/ You may be able to get you current file to open correctly by going through the import data wizard within excel: go to "Data" > "Import External Data" > "Import Data". This will then give you the option to set the seperating value within the data as a comma [ , ] which should correctly separate each field within the data file.

Cheers