How can I fix my Simpson Delta washing machine?

My Delta is not agitating properly. It seems like it is not on the spindle properly? There is not much agitation only me! I found two small similarly shaped pieces of plastic in the bowl and one other is still inside the agitator after i removed the filter. I can also tell there is something else maybe another piece under the agitator .How can I get it off to see if it has stipped or not.?