I have 2000C. To add an instrument, first add a staff by selecting the staff tool. Highlight (select) the staff above which you wish the new staff to appear. Click on the staff tool at the top of your screen to drop down the list and click "Add". A box will appear asking you how many new staffs you wish to create, say for now, 1, click OK. When the new staff appears, it will have a small box just to the left of the staff. (Left Click and hold down mouse button to drag this staff into position) Right click the box to open a dialog box. Click on "Edit Full Staff Name" to open a rather self-explanatory box where you type in the name of the staff.
click OK. I usually have to do a Cntrl-D screen redraw afterwards to see the name. Next, at the top of the screen, click on "Window", then click on "Instrument List'" to open that dialog box. In the left column you''ll see the name of your new staff. In the right column you'll see the names of instruments with a small arrow at the right hand side of the box. Click on this arrow to drop down a list of instruments and A) select one, or B) scroll up to the top and click on "New Instrument". From this new dialog box, select an instrument, give it a name and assign it a new MIDI channel. By the way, in the left column of staff names there is an arrow at the left side of the staff name box. Clicking this arrow will drop down a box that will allow you to use different instruments on different or the same MIDI channels for different layers, chords, etc.,. of the same staff. Hope this helps!!! Also, click on Help, Online Documentation, Index for one of the best instruction manuals I've ever encountered. You'll need Adobe Acrobat Reader. It's free on the Internet.