I could ask you to see the help online but instead of this I copy the information to you as following :
Setting attachment settings With the attachment settings, you determine how Service Desk will process attachments when users attach files to items. A third-party ftp server must be installed and configured with a user account and folder for Service Desk before you enter the attachment settings.
To set the attachment options: Choose System from the Tools menu. In the administrator console, select the System Panel node. Double-click the Attachment Settings icon in the view. In the Attachment Settings dialog box enter the following data: Enter the Name of the attachments server, the Username (account) and Password that Service Desk will use to connect to the server. Enter the path of the Target folder, this is the folder on the attachments server where the attachments are stored. It must exist before you configure these settings. Check the Use passive FTP if you do not want to use active FTP. Using passive FTP has the advantage of allowing firewalls to be set up between the application server and file server that open up specific ports for transfer and control. You can test the connection by clicking the Test connection button. Test connection creates a test directory on the file server, this test directory is named: test-. This may be needed when troubleshooting. The Save attachments in background check box allows background saving of attachments, the only advantage of this is that the user does not notice a delay when saving an item. This can be useful when the network connection is very slow, and waiting for the save function to complete would tie up the system for an inordinate length of time. Using this feature is not recommended except for slow connections. The system assumes the attachment will save successfully and no notification is given if the save fails. If the save action fails happens the attachment is lost and the situation will remain unnoticed until the file is recalled, and it cannot be retrieved.
Adding attachments An attachment can be any file. For example, you could attach the minutes of a meeting concerning a specific problem.
To add an attachment: Open the item to which you want to add an attachment. Click Attachment in the toolbar or choose Attachment from the Insert menu. Locate and select the file you want to add. All attached files are displayed in the attachment display at the bottom of the data form.
NOTE: Depending on your role's authorization, you can open, add or remove attachments of different items. Ask your system administrator for more information for which items you can open, add or remove attachments.
Im using this both to person than ServiceCall to attach any file, doc , txt or whatever I need.