The path on server is the pathname as it exists on the SQL Server machine. It cannot be a mapped drive and it must be physically on the SQL Server machine.
This is the pathname that you would see if you view the folder in windows explorer on the SQL Server machine itself - not on your local workstation. SQL Server is only able to access drives and folders that are physically on the SQL Server machine.
If the import folder is not located on the SQL Server machine or if you do not know this path, leave this field blank. Also, if the bulkadmin role has not been assigned to you on the SQL Server, then having this path will not help. When you click Import you will get a popup window regarding this field being blank, just click Continue.