If you're set with placing the .iso on your datastore...just place the .iso on your local workstation. Log in to ESX/i with vSphere Client. Right-click on the datastore you want to place the .iso on and select Datastore Browser. Click the 'Upload' toolbar icon and the explorer window will display. Browse to where you placed the .iso on your local workstation....select it...then click OK. It will then upload to the datastore.
See:
http://vmetc.com/2008/06/04/use-the-vi-client-datastore-browser-to-upload-files-to-esx-hosts/~coolsport00
