Type the function you wish to evaluate in on the command line.
i.e. NumSolver w^2-t

Numpad 1 Uses Euler's method
Numpad 2 Uses RK4 method
Numpad 3 Uses RKFelberg method

The input boxes don't quite work yet, so check for a new release.
Also, as of yet, there aren't any functions or parenthesis allowed
in the expressions.  This funtionality will be fixed in a
later release as well.