Yes, the Openbox menu is static (though it can have dynamic menus via pipes) by default, and does not add your newly installed must-have gadgets to your menu right away. you have to do that manually or find a script that can do it for you (like the debian menu).
Nope, you just installed it remember? It is now on your system and all you need is to ask the system to start the program. The commands are usually found in the /usr/bin folder on your computer, here you can see all of the commands you need to execute programs.
Just open a terminal (or press alt+f2) and write down the command you found in the /usr/bin and press enter, and your program should be running.
If it does not run, or you need it to run differently, write “man application_name” in the terminal and see if the manual gives you any clues.
Yes, and that's why we have the menu in the first place, so we don't have to type every command each time.
This can be done in crunchbang by a GUI menu editor or manually in the menu.xml-file in the /home/username/.config/openbox/ directory, either find the file and edit it with leafpad (or another editor of your choice) or go to the menu preferences>openbox config>GUI Menu editor and add your programs.
First press the “new item”-box and press your new item that appeared, you have to edit this. “Label” is the name you'll see in the menu, “ID” is not required when you just add programs, choose execute in the list and finally you write the command you start your application in the terminal. Then save and exit, reconfigure the menu and it'll be there you wanted to be.