Start off by installing the standalone Tcl/Tk version of ProB. Follow the instructions in Installation.
Start ProB by double-clicking on ProBWin (for Windows users), or by launching StartProB.sh from a Terminal (for Linux and Mac users).
Mac users may also be able to launch ProB by double-clicking on StartProB.sh.
This should bring up a window as follows (on a Mac):
In case this does not work, please have a look at the output of ProB in the terminal window (on Windows a separate window will be automatically started) and send us a description of what is printed in that window along with a detailed report (which operating system do you use, which version of it, which version of ProB have you downloaded, ...). Normally, it should look as follows (on Windows):
Use the "Open..." command in the "File" menu
and then navigate to the "Examples" directory that came with your ProB installation:
Inside the samples folder, open the "Lift.mch" machine. Your main ProB window should now look as follows:
We have now loaded a first simple B model. Let us look at the contents of the ProB window (ignoring the menu bar).
Now, double click on "INITIALISATION(4)" in the "Enabled Operations" Pane. This has the effect of executing the initialisation and moving the machine into its initialised state: