You can set breakpoints by clicking in the left margin on a line number. Most of the TotalView GUI is self-explanatory. You select things with the left mouse button, bring up an action menu with the middle button, and ``dive'' into functions, variables, structures, processes, etc., with the right button. Pressing cntl-? in any TotalView window brings up help relevant to that window. In the initial TotalView window it brings up general help. The full documentation (The TotalView User's Guide) is available at http://www.etnus.com/tw/tvdemo37.htm CHECK.
You switch from viewing one process to the next with the arrow buttons at the top-right corner of the main window, or by explicitly selecting (left button) a process in the root window to re-focus an existing window onto that process, or by diving (right button) through a process in the root window to open a new window for the selected process. All the keyboard shortcuts for commands are listed in the menu that is attached to the middle button. The commands are mostly the familiar ones. The special one for MPI is the ` m' command, which displays message queues associated with the process.
Note also that if you use the MPI-2 function MPI_Comm_set_name on a communicator, TotalView will display this name whenever showing information about the communicator, making it easier to understand which communicator is which.