Don`t panic (at least, not unless you like panicking). You don`t have to have a bean trench, and you`ll be able to grow quite a reasonable crop without one, but the beans won`t be as plentiful or as good, and of course we all like to grow more and bigger beans than anyone else so that we can brag about it on these boards.
And as for using all the funny little gadgets .. ....
JUST TYPE BETWEEN THE SQUARE BRACKETS