After I pick to add an Instrument Track, I just double click in the box and it will open the Sequencer?

Opening the MIDI editor will depend on a few things.

[*]Click a MIDI track with no parts selected and select Open Drum Editor from the MIDI menu.[*]Double-click a part to open it in the default editor. Which editor opens depends on the settings in the Preferences (Event Display–MIDI page)[*]Double-clicking will open the editor selected on the Default Edit Action pop-up menu. However, if the option ‘Edit as Drums when Drum Map’ is assigned is activated and a drum map is selected for the edited track, the Drum Editor will open.

If you’re just beginning to create your drum track, the first method would be preferred. As you go and want to edit stuff, personally, I use the 3rd method [load the EZD drum map and check the ‘Edit as Drums when Drum Map’ in the Preferences (Event Display–MIDI page)]. It makes it quick to switch between the drum editor without having to think too much.