Answer by Albert Gonzalez for How to start up xmonad with apps on other workspaces

You can spawn the app via startupHook and then use a manageHook to handle window placement.

manageHook such as:

, className =? "deluge" --> doShift ( myWorkspaces !! 3 )

The above will actually spawn deluge on Workspace 4. In my startupHook I have

spawnOnce "deluge-gtk" to launch the app on start-up.

You would want to import XMonad.Util.SpawnOnce. doShift comes from the default XMonad.ManageHooks You could also take a look at XMonad.Actions.SpawnOn but I only use manageSpawn from that module.