to use the table tool Go to table->clear used table. a box will appear asking you how many generations to calculate. enter a number then click OK.
you can use ctrl-g to switch between viewing the current generation and the next generation.
when you view the next generation, you can draw the next pattern by clicking the cells with squares on them.
when you view the current generation, just the rule table entries get changed when you click on the cells
a tiny square in the rule table means the entry has not been used yet. a big square in the rule table means the entry will be use for the first time when it calculates the next generation.