It should have been setup and configured during your LANDesk installation and configuration. If not you can create a folder and assigned it the correct permission and use it as the default location for all your future package. Otherwise you can look at your core file and folder share and see which folder was set up as the location for your package.
You can set this inside your Packages and if you are using the Landesk Replication
under Configure - Preferred Server - Sources.
If you don't have an existing repository, the EASIEST location is to create a Packages folder under your LDlogon share. That location will be accessible for both UNC and URL package deployments. The LDLogon share is located on the drive where LANDesk is installed (ex. D:\Program Files (x86)\LANDesk\ManagementSuite\ldlogon). IIS is already sharing out this location so you don't need any additional configuration. Confirm that there is sufficient disk space on this drive before making it your main package repository. Often times you need to have an external repository. If you need an external repository, you need to ensure that the external server is running IIS and has the same share, NTFS, and IIS settings as your core server....probably too big of a discussion here....the install guide would be a good starting point but as previously mentioned, that should have already been configured by your vendor.
A good hint to where your software repository resides is to edit an existing distribution package (if you have one) and see where it resides. If you have none at all,well.... then see above.